Tuning luminescence in gold(I)-phosphine complexes: structural, photophysical, and theoretical insights

Abstract

Gold(I) complexes featuring phosphine ligands functionalized with chromophores such as triphenylene, phenanthrene, and carbazole were synthesized and systematically studied to explore the relationship between molecular structure and luminescence properties. Comprehensive photophysical characterization revealed that the coordination environment and chromophore positioning significantly influence intersystem crossing, phosphorescence, and aggregation behavior. In solution, aggregation-induced phenomena were probed using computational tools, including density functional theory (DFT) and noncovalent interaction (NCI) analysis, revealing diverse π-stacking and Au⋯π interactions. Distinct photophysical trends were identified among the three series of compounds, with triphenylene derivatives exhibiting aggregation-induced emission broadening and phenanthrene derivatives showing strong heavy atom effects. The combination of experimental and theoretical insights provides a foundation for designing luminescent materials with tunable properties for optoelectronic applications.

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Introduction

Gold(I) complexes have been extensively studied for their unique luminescent properties, which arise from various electronic transitions including metal-centered transitions and ligand-to-metal charge transfer (LMCT). They are frequently affected by the presence of metal⋯metal contacts, usually known as aurophilic interactions. These photophysical properties make gold(I) complexes attractive candidates for applications in optoelectronic devices, sensors, and bioimaging, among others.^1–12 Traditionally, phosphine ligands have been widely employed in the coordination sphere of gold(I) complexes due to their strong σ-donating abilities. However, the luminescence of such complexes typically arises from other ligands coordinated to the metal center, with phosphine playing a more structural or electronic role rather than contributing to the emissive properties.^13–18

Recent advances in ligand design have demonstrated that phosphine ligands can be functionalized with chromophores to exhibit intrinsic luminescent properties.^19–25 Phosphines containing extended aromatic chromophores have been shown to display intrinsic fluorescence due to their extended π-conjugation and favorable photophysical characteristics, including high quantum yields and photostability.^26–30 These functionalized phosphine introduce a novel approach to luminescent gold(I) complexes, where the phosphine itself can participate in or enhance the overall emission and self-assembling processes.

This study focuses on the synthesis and photophysical characterization of gold(I) complexes containing luminescent phosphine ligands, where the chromophore is either positioned on the phosphine ligand, on a second coordination ligand, or on both. This will have direct applications in tuning the emissive properties of these metal complexes and will provide foundational insights into how luminescence can be tuned in materials more generally.

The impact of the chromophore's location on the photophysical behavior of the gold(I) complexes is herein systematically explored, with a particular emphasis on intersystem crossing (ISC), and the influence of intermolecular weak interactions such as π–π stacking and aurophilicity.^8,22

Several gold(I) complexes featuring chromophore-functionalized phosphines were synthesized and characterized in this work, to evaluate the impact of the chromophore location on their structural and photophysical properties. In addition, density functional theory (DFT) calculations were performed to provide insights into the electronic structure, intersystem crossing mechanisms, and aggregation in solution. By integrating experimental and theoretical approaches, this study aims to establish structure–property relationships that can guide the design of novel luminescent materials for advanced applications in optoelectronics and sensing.

Results and discussion

Synthesis and characterization

Three series of gold(I) compounds which differ in the type of chromophore and the position of coordination of the gold(I) atom have been synthesized following the procedure displayed in Scheme 1. Three series of compounds have been synthesized that have been named as series 1 (those containing triphenylene, Triphen, as ligand), series 2 (those containing phenanthrene, Phen, as ligand) and series 3 (those containing carbazole, Cz). It requires the previous preparation of different phosphine ligands (PR₃) according to the reported procedure^21,31 for the lithiation of the corresponding aromatic halide followed by the addition of the chlorophosphane (see Scheme S1†). After chromatographic purification, the desired ligands P1 containing triphenylene (Triphen), P2, with phenanthrene (Phen), and P3, with carbazole (Cz), were obtained as white powders. Subsequently, the [AuCl(PR₃)] precursors were obtained in good yields by simple reaction with a stoichiometric amount of [AuCl(tht)] (tht = tetrahydrothiophene), as the gold(I) source, and the corresponding phosphine (Scheme S1†). The correct formation of the compounds was evidenced in the ³¹P{¹H} NMR spectra where the phosphorus signal showed a downfield shift (20–30 ppm) with respect to the corresponding free phosphine.

Scheme 1 Synthetic procedure of the phosphine gold(I) complexes. Reaction conditions: 1a, 2a, 1b, 2b, 3b, 1c, and 2c: 5 days reaction at RT; 3a: KOH, 1 h in MeOH and 3c: K₂CO₃, 24 h reaction in CH₃(CO)CH₃ at RT.

The [AuCl(PR₃)] compounds were used as precursors to synthesize a wide variety of gold(I) compounds that differ on: (1) having the chromophore linked directly to the Au(I) metal centre (1–3a); (2) having a chromophore at the phosphine unit (1–3b); (3) having the chromophore in both coordination positions (1–3c), opening a wide variety of exhibiting possibilities in the field of luminescent gold(I) compounds. In particular, we aim at exploring the effect of the heavy atom effect on the T₁ population of the chromophores depending on their structural coordination position.

These gold(I) complexes were synthesized with slight modification of a previously reported method (see Scheme 1).^32–35

In the case of series 1, 2, and 3b, a solution of the organoboronic acid or the pinacol ester and the corresponding [AuCl(PR₃)] precursor in the presence of excess caesium carbonate as a base was maintained under stirring in isopropanol at RT for 5 days under inert atmosphere. Then the solvent was evaporated, and the final product was extracted with dichloromethane. In the case of complexes 3a and 3c a carbazole solution and the [AuCl(PR₃)] were stirred in the presence of a base.

The compounds were characterized by ¹H, ³¹P{¹H} and ¹³C{¹H} NMR, as well as by 2D ¹H–¹H COSY and ¹H–¹³C HSQC NMR and IR spectroscopy techniques and mass spectrometry (see Fig. S1–S53†). The ¹H NMR spectra show the signals of both the chromophore and phosphine moieties with the expected integration. As expected by the chemical equivalence of the phosphorus atoms, the ³¹P{¹H} NMR spectra show only one signal whose chemical shift appears slightly downfield shifted (5–10 ppm) with respect to that of the [AuCl(PR₃)] precursor, which is an indication of the successful formation of pure products.

Single crystals suitable for X-ray diffraction analysis were successfully grown for 1a, 1b, 3a, and 3b from slow diffusion of hexane into dichloromethane solutions of the complexes at room temperature. The corresponding molecular structures are presented in Fig. 1 and the selected bond lengths and angles are summarized in Table 1. Linear coordination of ligands at the Au(I) centers is observed, with P–Au–C angles of 177.6°(1), 172.5°(1) and 178.8°(7) for 1a, 1b and 3b, respectively and 171.9°(2) for 3a. No aurophilic contacts are observed in any of the structures (Fig. 2).

Fig. 1 X-ray crystal structures of 1a (a) 1b (b), 3a (c), and 3b (d). Yellow: gold; orange: phosphorus; blue: nitrogen and grey: carbon. All hydrogens have been omitted for clarity.

Fig. 2 3D crystal packing of complex 1a (a), 1b (b), 2a (c), 3a (d) and 3b (e). The crystal structure of 2a was published previously by us in ref. 36 and has been included for comparison purposes.

Table 1 Selected bond lengths (Å) and angles (°) for 1a, 1b, 3a, and 3b

1a
Distance	(Å)	Angle	(°)
Au(1)–C(1)	2.054(3)	C(1)–Au(1)–P(1)	177.6(1)
Au(1)–P(1)	2.297(9)	Au(1)–P(1)–C(21)	112.6(1)
P(1)–C(21)	1.816(4)
1b
Distance	(Å)	Angle	(°)
Au(1)–C(1)	2.058(4)	C(1)–Au(1)–P(1)	172.5(1)
Au(1)–P(1)	2.299(1)	Au(1)–P(1)–C(11)	110.3(1)
P(1)–C(11)	1.816(4)
3a
Distance	(Å)	Angle	(°)
Au(1)–N(1)	2.018(7)	N(1)–Au(1)––P(1)	171.9(2)
Au(1)–P(1)	2.236(2)	Au(1)–P(1)–C(21)	107.0(3)
P(1)–C(21)	1.800(1)
3b
Distance	(Å)	Angle	(°)
Au(1)–C(1)	2.046(3)	C(1)–Au(1)–P(1)	178.8(7)
Au(1)–P(1)	2.286(7)	Au(1)–P(1)–N(11)	111.78(7)
P(1)–N(11)	1.707(2)	Au(1)–P(1)–N(31)	114.84(8)
P(1)–N(31)	1.701(2)
P(1)–C(51)	1.790(3)

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The 3D packing of complexes displays a conformation driven by the establishment of C–H⋯π interactions between a π ring of the chromophore and the phosphine moieties (2a,³⁶3a, and 3b) or between different phosphine moieties (1a and 1b). Moreover, the packing of 1b shows the superposition of the triphenylene in a staggered conformation and causes π–π stacking (distances of 3.115 Å for 1b and 4.759 Å for 3b). When comparing the dimers in series 1, it is observed that the chromophore, when linked to the phosphine moiety, is capable of stacking and forming π–π interactions. In contrast, when the chromophore is directly attached to the Au(I) center, π–π stacking is not observed. In series 3, however, π–π interactions are present in both scenarios: when the gold atom is bound to the chromophore and when it is bound to a phenyl group. This indicates that, regardless of the structural configuration around the gold atom, the carbazole unit retains its ability to establish π–π interactions (Fig. 2 and S54–S58–S52†).

Photophysical characterization

Absorption and emission spectra were recorded in 1 × 10⁻⁵ M dichloromethane solutions for the three series of complexes and the results are summarized in Table 2. The absorption spectra of all compounds exhibit typical bands in the 230–310 nm range due to π–π* intra-ligand transitions corresponding to the different chromophores (see Fig. S59†).^20,36,37 The shape and position of these bands for the gold(I) complexes and their free phosphine ligands P1–P3 are very similar in all cases. The TD-DFT calculations performed at the CAM-B3LYP(dcm)/def2-TZVP//RI-BP86-D4/def2-TZVP level of theory for the three series of compounds demonstrate a reasonable agreement between the observed and calculated absorption bands (see Table 2). As an example, the computed spectrum of compound 1a is shown overlapped with the experimental spectrum in Fig. 3. Both spectra exhibit a similar band structure, with the calculated bands consistently blue-shifted by 20–30 nm relative to the experimental ones.

Fig. 3 (a) Experimental and theoretical UV-vis spectra of compound 1a with indication of the main excitations responsible for the band. (b) NTOs corresponding to the lowest energy band. (c) NTOs corresponding to the S₀ → S₅ excitation. The theoretical excitation energies and oscillator strengths are indicated.

Table 2 Absorption and emission data of the different series of the compounds in dichloromethane at 1 × 10⁻⁵ M and ratio of phosphorescence and fluorescence intensities, I_P/I_F, in N₂-sat solutions. Excitation energies associated transition and oscillator strength and Singlet–triplet (S₁–T₁) gap are given at the CAM-B3LYP(solvent = CH₂Cl₂)/def2-TZVP//RI-BP86-D4/def2-TZVP level of theory

Cmpnd	Absorption λmax, nm (ε × 10^4 M^−1 cm^−1)	Fluorescence emission air-equilibrated λmax (nm)	Phosphorescence emission N2-saturated λmax (nm)	I P/IF RT (77 K)	Excitation Energy and oscillator strength	S1–T1 gap
P1	266 (8.35), 314 (1.54)	363	—	−(0.36)	—
AuCl(P1)	271 (6.48), 314 (0.98)	371	462	2.2 (13.1)	—
1a	272 (5.91), 309 (1.45)	381 (3.25 eV)	459 (2.70 eV)	14.1 (12.1)	S0 → S1 4.23 eV (293 nm) f = 0.0030	0.57 eV
1b	268 (1.77), 311 (3.77)	381 (3.25 eV)	460 (2.69 eV)	3.0 (19.7)	S0 → S1 4.22 eV (294 nm) f = 0.0180	0.46 eV
1c	267 (8.84), 314 (1.08)	372 (3.33 eV)	463 (2.68 eV)	0.9 (24.2)	S0 → S1 4.22 eV (294 nm) f = 0.0085	0.99 eV
P2	255 (5.73), 300 (92.7)	372	—	−(2.6)	—
AuCl(P2)	261 (5.26), 309 (1.06)	374	496	0.9 (15.7)	—
2a	255 (6.05), 313 (1.63)	368 (3.37 eV)	500 (2.48 eV)	7.5 (112.3)	S0 → S1 4.16 eV (298 nm) f = 0.0109	0.48 eV
2b	254 (9.05), 313 (2.12)	378 (3.28 eV)	501 (2.47 eV)	4.2 (29.8)	S0 → S1 4.20 eV (295 nm) f = 0.0068	0.39 eV
2c	261 (4.64), 308 (1.00)	372 (3.33 eV)	496 (2.50 eV)	1.3 (46.4)	S0 → S1 4.16 eV (298 nm) f = 0.0115	1.09 eV
P3	235 (8.13), 288 (2.30)	380	—	−(9.8)	—
AuCl(P3)	231 (11.17), 288 (2.82)	371	—	−(10.5)	—
3a	237 (6.77), 293 (1.36)	347 (3.57 eV)	—	−(43.8)	S0 → S2 4.23 eV (293 nm) f = 0.1193	0.99 eV
3b	233 (13.10), 291 (3.74)	347 (3.57 eV)	—	−(9.8)	S0 → S3 4.52 eV (274 nm) f = 0.0397	0.41 eV
3c	233 (8.92), 291 (3.73)	346 (3.58 eV)	—	−(4.6)	S0 → S3 4.36 eV (284 nm) f = 0.1520	1.23 eV

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The lowest-energy transition band comprises two excitations (S₀ → S₁ and S₀ → S₂), with the natural transition orbitals (NTOs) depicted in Fig. 3b. These NTOs reveal that the transitions correspond to a π → π* charge transfer. The next observable band, associated with the S₀ → S₅ excitation, displays a mixed intra-ligand charge transfer (ILCT) and ligand-to-metal charge transfer (LMCT) character.

The possibility of aggregation of the compounds in solution has been analyzed for selected examples. Given the richness in aromatic rings and the variety of possible conformations and aggregation modes, we focused on the structures depicted in Fig. 1. Initially, aggregation in the solid state was analyzed to identify potential dimeric assemblies. The most stable dimer from the solid-state analysis was selected as a starting point for optimization in solution using a continuum model with dichloromethane (DCM) as the solvent. Frequency calculations were performed to confirm the minimum-energy nature of the assemblies and to compute the free energies of complexation relative to the isolated monomers. Additionally, the noncovalent interactions contributing to dimer formation were visualized in real space using noncovalent interaction plots (NCIplot), as shown in Fig. 4.

Fig. 4 Optimized geometries (RI-BP86-D4/def2-TZVP) of the dimers of 1a (a), 1b (b), 2a (c), 3a (d), and 3b (e). Free Gibbs energies for the dimerization in dichoromethane are also indicated. The setting for the NCIplot representation are RDG = 0.5, ρ cut-off = 0.05, color scale −0.04 a.u. ≤ (sign λ₂)ρ ≤ −0.04 a.u.

The results reveal that centrosymmetric dimers are formed in compounds where the Au atom is bonded to a phenyl group (1b and 3b) or phenanthrene group (2a). These dimers are stabilized by a combination of π-stacking interactions between the aromatic rings of the triphenylene, phenanthrene and carbazole chromophores and CH⋯π interactions involving the C–H bonds of these chromophores and the π-system of either the phenyl ring (in 1b) or the carbazole (Cz) ring (in 3b). In case of 2a, the C–H⋯π contacts are established between tha H-atoms of the phenyl ring and the phenanthrene's π-system. These interactions are clearly visible as large green reduced density gradient (RDG) isosurfaces in the NCIplot. In contrast, when the triphenylene or carbazole chromophore is directly connected to the Au center (as in 1a and 3a), the assemblies are more complex and exhibit less symmetric dimers.

The NCIplot for these compounds indicates that π-stacking interactions are still dominant, but additional forces, such as Au⋯π and Au⋯C interactions, also play a significant role in stabilizing the dimers. The free energy of formation of the dimers is highly negative in all cases, suggesting that these dimers are most likely present in solution, even at low concentrations. This highlights the significant role of noncovalent interactions, including π-stacking, CH⋯π, and metal-involved contacts, in driving the aggregation behavior of these compounds.

The significant broadening observed in the spectra of the triphenylene-based compounds (series 1, Fig. S59†) can be attributed to the formation of aggregates in solution. This behavior is likely due to the exposure and preorganization of the triphenylene units in the dimer, facilitating oligomer formation. In contrast, the geometries of the dimers in series 3 (Fig. 4c and d) suggest a lack of preorganization in solution, which may hinder the formation of extended aggregates. A similar lack of preorganization is observed in the optimized geometry of dimer 2a, represented in Fig. 4c. These findings indicate that series 1 is inherently more predisposed to form larger supramolecular assemblies, likely due to the structural alignment and interaction potential of the triphenylene core.

Emission spectra were recorded upon excitation the samples at the absorption maxima and at air-equilibrated and nitrogen saturated solution conditions (Fig. 5). All compounds display a vibronically structured emission band corresponding to the ¹IL emission of the chromophore.^38,39 A second broad emission band at ca. 520 nm is recorded for P1, ascribed to the corresponding triphenylene excimer.^40,41

Fig. 5 Emission spectra of (a) series 1 air-equilibrated conditions; (b) series 1 N₂-saturated conditions; (c) series 2 air-equilibrated conditions; (d) series 2 N₂-saturated conditions (e) series 3 air-equilibrated conditions (f) series 3 N₂-saturated conditions of 1.0 × 10⁻⁵ M dichloromethane solutions, λ_exc = 310 nm.

Several trends can be retrieved in all three series of compounds, both in air-equilibrated and N₂-saturated samples. The triphenylene (series 1) and phenanthrene (series 2) derivatives exhibit similar behavior, which is distinct from the carbazole compounds and will be discussed then separately. Regarding series 1 and 2, fluorescence emission bands can be observed for all compounds in air equilibrated conditions (including P1 and P2 and the [AuClPx] precursors), with the free phosphines P1 and P2 being those presenting higher fluorescence intensity (Fig. 5). The presence of the gold(I) heavy atom induces a significantly stronger reduction in fluorescence emission, that is associated to the increase in the population of the triplet excited state (see Table 2), as confirmed by the increase in ratio between phosphorescence and fluorescence (I_P/I_F).

Compounds 2a and 2b exhibit smaller S₁–T₁ gaps compared to compounds 1a, 3a and 1b, 3b, respectively. In the case of 2c, the S₁–T₁ gap is smaller than that of 3c but slightly larger than 1c. This suggests that while the S₁–T₁ gap plays a key role, it is not the sole factor influencing emission behavior, since aggregation effects may also contribute significantly to the triplet to singlet population ratio. In fact, the HOMO–LUMO gap is reduced in the dimers (0.28–0.45 eV) in comparison with the monomers, see Table S5.† The fluorescence emission intensity of 3a–3c follows the order 3a > 3c > 3b both in air-equilibrated and N₂-saturated samples, in agreement with the recorded quantum yields (Table 3). Furthermore, in solution the carbazole series does not exhibit phosphorescence however display a blue shift in the emission (385 to 356) respect to the free ligand.

Table 3 Luminescence quantum yields recorded for all the compounds in dichloromethane

Compound	Air-equilibrated samples		N2-saturated samples		77K^a
	Φ Fl	Φ Ph	Φ Fl	Φ Ph	Φ Ph
a Φ Ph calculated considering the Ph/Fl ratio and assuming that ΦFl (RT) ∼ ΦFl (77 K).
P1	0.04	—	0.04	—	0.01
AuCl(P1)	0.01	—	0.01	0.02	0.13
1a	0.01	—	0.01	0.08	0.12
1b	0.01	—	0.01	0.02	0.20
1c	0.01	—	0.01	0.03	0.24
P2	0.01	—	0.08	—	0.03
AuCl(P2)	0.01	—	0.01	0.05	0.16
2a	0.01	—	0.01	0.09	0.12
2b	0.01	—	0.01	0.03	0.30
2c	0.01	—	0.01	0.07	0.46
P3	0.03	—	0.03	—	0.29
AuCl(P3)	0.01	—	0.02	—	0.11
3a	0.14	—	0.19	—	0.14
3b	0.03	—	0.11	—	0.29
3c	0.09	—	0.13	—	0.41

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All compounds (including precursors P1–P3) display almost only phosphorescence emission (fluorescence being suppressed) at low temperatures (see Fig. S60†). Under these conditions each series shows a considerable increase in the phosphorescent quantum yield at 77 K, where non-radiative mechanisms are less efficient. In particular, for series 1, the complex 1c shows the highest quantum yield. In series 2 and 3 the highest yields are for complexes 2a and 3a in good agreement with the theoretical calculations, where type a and b complexes present a smaller energy gap (Table 3). These results provide a key insight: the presence of emissive chromophores on both parts of the gold(I) complex does not enhance the sample's emissive properties. Furthermore, a smaller energy gap is observed for type a complexes, making emission more favorable when the chromophore is directly coordinated to the metal center.

A new emission band at longer wavelengths appears in all gold(I) complexes from series 1 and 2 when the oxygen is removed from the solution generating a dual emission (Fig. 6). The large Stokes’ shift and the vibronically structured shape provide sufficient corroboration to assign this second band to the phosphorescence metal perturbed ³IL transitions. This band is not present for P1 and P2 due to the absence of the heavy metal center, responsible for the ISC and T₁ population.^33,42,43

Fig. 6 Emission spectra of (a) series 1 air-equilibrated conditions (b) series 1 N₂-saturated conditions (c) series 2 air-equilibrated conditions (d) series 2 N₂-saturated conditions of PS matrix. Air-equilibrate samples were normalized at the fluorescence maxima.

The phosphorescence emission is more pronounced for the a and c derivatives (as indicated by the I_P/I_F ratio), due to the direct bonding of the heavy metal to the polyaromatic chromophore, which enhances intersystem crossing (ISC) and facilitates T₁ state population. That is, phosphorescence emission can be enhanced by the direct coordination of an emissive chromophore to the metal center.

Lifetimes are in the order of a few ns for the fluorescence and hundreds of μs for the corresponding phosphorescence (Table S6†).

In depth investigations on the photophysical properties of the compounds can be done trying to reduce non-radiative processes at room temperature, upon immobilization of the samples in a polymer matrix, such as PS. Interestingly, dual emission is already observed in air-equilibrated samples of Series 1 and 2, unlike in solution (with 1a and 2a being the compounds with higher emission phosphorescence intensity), and the emission becomes completely shifted to pure phosphorescence at room temperature when the oxygen is removed from the environment (Fig. 6).

In the case of carbazole derivatives, the gold complexes 3a and 3b display phosphorescence at room temperature (under N₂-saturated conditions, Table S7†) which is more favored for 3a. That means that the competition of internal conversion to ground overrules the radiative pathway for triplet decay, in solution, leading to the absence of phosphorescence. In the polymeric matrix the vibrations are decreased and the radiative pathway for triplet emission becomes competitive restoring phosphorescence.

The quantum yields of all compounds display higher efficiency in the PS films compared to the solutions, confirming that the decrease in internal conversion deactivation pathways for both singlets and triplets due to the decrease in vibrational motions (Table 4). An increase of up to two orders of magnitude in the phosphorescent emission in N₂-saturated conditions is observed, in accordance with much longer lifetimes values recorded.

Table 4 Photophysical parameters of PS matrix samples

Quantum yields					Luminescence lifetimes
Compound	Air-equilibrated samples		N2-saturated samples		Air-equilibrated samples		N2-saturated samples
	Φ Fl	Φ Ph	Φ Fl	Φ Ph	τ Fl (ns)	τ Ph (μs)	τ Fl (ns)	τ Ph (μs)
a Not possible to measure
AuClP1	0.01	<1%	0.01	0.14	14.2	361	—
1a	<1%	0.01	<1%	0.13	21.1	64	—	526
1b	0.01	0.01	0.01	0.15	12.9	280	—	1239
1c	0.01	0.03	0.01	0.41	18.2	147	—	905
AuClP2	0.01	0.01	0.01	0.09	26.0	263	—
2a	<1%	0.03	0.02	0.05	43.9	77	—	588
2b	0.01	0.01	0.01	0.30	26.5	187	—	1802
2c	0.02	0.02	0.02	0.24	38.3	62	—	819
AuClP3	0.03	—	0.01	0.01	17.9	—	—
3a	0.03	—	0.03	0.02	10.1	—	—	324
3b	0.02	—	0.01	0.01	27.7	—	—
3c	0.03	—	0.01	<1%	10.4	—	—

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Conclusions

This study presents a comprehensive investigation into the synthesis, structure, and photophysical properties of gold(I) complexes featuring chromophore-functionalized phosphine ligands. Single-crystal X-ray diffraction confirmed their linear coordination geometries and diverse intermolecular interactions.

A correlation is observed between the crystal structures and the interactions predicted by theoretical calculations. This suggests that when the emissive chromophore is located within the phosphine moiety, centrosymmetric dimers featuring π–π interactions are formed. In contrast, in other configurations, the resulting dimers are less ordered. Therefore, for aggregation studies, it is essential that the structures incorporate chromophores within the phosphine moiety to facilitate these interactions.

Photophysical characterization revealed that luminescence behaviors are heavily influenced by the chromophore type and its coordination environment, with phenanthrene derivatives exhibiting the strongest heavy atom effects, as evidenced by reduced fluorescence intensities and enhanced triplet-state populations. DFT studies corroborated the experimental findings, demonstrating that electronic transitions, S₁–T₁ gaps, and aggregation phenomena significantly impact the observed emission properties. The combination of experimental and computational approaches provides a robust framework for understanding the role of gold(I) in tuning photophysical properties. Future work may explore the potential of these compounds in optoelectronic devices and as models for studying metal-induced photophysical processes.

Experimental section

General procedures

All manipulations have been performed under prepurified N₂ using standard Schlenk techniques. Solvents have been distilled from appropriate drying agents. Commercial reagents 2-bromotriphenylene, 9-phenanthreneboronic acid, carbazole and phenylboronic acid were purchased from Aldrich and used as received.

Physical measurements

Infrared spectra were recorded using a FT-IR 520 Nicolet Spectrophotometer. ¹H NMR (δ (TMS) = 0.0 ppm) and ³¹P{¹H} NMR (δ (85% H₃PO₄) = 0.0 ppm) spectra were recorded at 400 or 500 MHz using Varian and Bruker spectrometers at 25 °C (Centres Científics i Tecnològics, Universitat de Barcelona). In the assignation of NMRs spectra, signals denoted with * correspond to the chromophore unit directly linked to the gold(I) metal centre. ES(+) mass spectra were recorded on a Fisons VG Quatro spectrometer (Centres Científics i Tecnològics, Universitat de Barcelona). Absorption spectra were obtained in a 10 mm quartz cuvette in dichloromethane on a Varian Cary 100 Bio UV Spectrophotometer. The emission spectra of the compounds in solution were obtained in a fluorescence quartz cuvette of 10 mm path length, using a Horiba-JobinYbon SPEX Nanolog Spectrofluorimeter (Universitat de Barcelona). Quantum yields have been recorded on Absolute PL quantum yield spectrometer from Hamamatsu Photonics upon excitation the samples at 300–310 nm. Luminescence lifetimes were measured on a JYF-DELTAPRO-NL equipment upon excitation of the samples with a 284 nm NanoLED and collecting the decays through a bandpass filter of 400, 500, or 550 nm, depending on the emission maximum. The best fittings correspond to biexponential decays, and the indicated values correspond to the average considering the respective amplitudes.

The single crystal X-ray data for all crystals were collected at 120 K using an Agilent SuperNova diffractometer with a HyPix-Arc 100 detector using mirror-monochromated Cu-Kα (λ = 1.54184 Å) radiation. The structures were solved by intrinsic phasing (SHELXT)⁴⁴ and refined by full-matrix least squares on F² using Olex2,⁴⁵ utilizing the SHELXL module.⁴⁶ Anisotropic displacement parameters were assigned to non-H atoms and isotropic displacement parameters for all H atoms were constrained to multiples of the equivalent displacement parameters of their parent atoms with U_iso(H) = 1.2 U_eq(C) of their respective parent atoms. The crystal data and experimental details for the data collections of 1a, 1b, 3a, and 3b are given in Tables S1–S4,† respectively. Deposition numbers 2409503 (1a), 2409504 (1b), 2409505 (3a), and 2409506 (3b)† contain the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe Access Structures service.

Theoretical methods

The geometries of all compounds in this study were fully optimized at the RI-BP86-D4/def2-TZVP level of theory⁴⁷ (a–d) using the Turbomole 7.7 program.⁴⁸ Frequency calculations were conducted for both monomers and dimers to confirm their true minimum nature and to estimate entropic contributions. Gibbs free energies were calculated at room temperature. Solvent effects (dichloromethane, DCM) were accounted for using the COSMO model,⁴⁹ a variant of dielectric continuum solvation models. Time-dependent DFT (TD-DFT) calculations were performed to compute 100 excited states using the CAM-B3LYP functional⁵⁰ using the ORCA 5.0 program,⁵¹ with solvent effects incorporated via the CPCM solvation model.⁵² The gold's basis set used effective core potential with scalar relativistic effects (RECP).⁵³

Synthesis and characterization

Synthesis of phosphine ligands.
Diphenyl(triphenylen-2-yl)phosphane (P1). The synthesis of P1 refers to literature reports.¹ A solution of 2-bromotriphenylene (0.359 g, 1.17 mmol) in 10 mL of THF was cooled to −78 °C and n-butyllithium (0.80 mL, 1.25 mmol) was added and stirred for 1 h. Next, P(Ph)₂Cl (0.20 mL, 1.28 mmol) was added dropwise. After stirring 1 h at −78 °C the refrigeration was stopped, and the reaction mixture was stirred overnight. Subsequently deionized water (20 mL) was added and THF was removed by reduced pressure evaporation. The resulting aqueous phase was extracted with dichloromethane (3 × 20 mL). Then the combined organic phase was dried over anhydrous sodium sulfate. The solvent was evaporated, and the crude oil obtained was purified by silica gel column chromatography and DCM/Hex (2 : 3). Yield 31%. ¹H NMR (400 MHz, CDCl₃, ppm): δ 8.68–8.58 (m, 5H), 8.40 (ddd, J = 8.0, 1.5, 0.8 Hz, 1H), 7.70–7.51 (m, 6H), 7.45–7.35 (m, 9H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ −4.92. MALDI-TOF(+) m/z: 413.142 ([M + H]⁺, calcd 413.1454). IR (, cm⁻¹): ν(=C–H) 3059, ν(C=C) 1436, δ(C–H Ph) 727–680 cm⁻¹.
Phenanthren-9-yldiphenylphosphane (P2). The synthesis of P2 was performed by following the same procedure as P1 but using 9-bromophenanthrene (0.300 g, 1.17 mmol) and for chromatographic purification DCM/Hex (1 : 4) was used. Yield 37%. ¹H NMR (400 MHz, CDCl₃, ppm): δ 8.73 (d, J = 7.5 Hz, 1H), 8.68 (d, J = 7.8 Hz, 1H), 8.47–8.43 (m, 1H), 7.68–7.60 (m, 3H), 7.56–7.49 (m, 2H), 7.41–7.32 (m, 10H), 7.24 (d, J = 5.2 Hz, 1H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ −12.94. MALDI-TOF(+) m/z: 363.101 ([M + H]⁺, calcd 363.1297). IR (, cm⁻¹): ν(=C–H) 3060, ν(C=C) 1435, δ(C–H Ph) 740–687 cm⁻¹.
9,9′-(Phenylphosphanediyl) bis (9H-carbazole) (P3). The synthesis of P3 refers to literature reports.² A solution of carbazole (0.520 g, 3.11 mmol) in 10 mL of THF/Hex (1 : 1) was cooled to −78 °C and n-butyllithium (2.0 mL, 3.20 mmol) was added and stirred for 1 h. Next, the temperature was allowed to warm up to −20 °C and PPhCl₂ (0.21 mL, 1.55 mmol) was added dropwise. After stirred for 1 h the refrigeration was stopped, and the reaction mixture was stirred overnight. The solvent was removed under vacuum and the white solid obtained was purified by silica gel column chromatography (30% DCM–70% Hex). Yield 52%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.05–8.00 (m, 4H), 7.60–7.55 (m, 4H), 7.54–7.48 (m, 3H), 7.46–7.41 (m, 2H), 7.30–7.23 (m, 8H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 51.80. MALDI-TOF(+) m/z: 441.1203 ([M + H]⁺, calcd 441.1515). IR (, cm⁻¹): ν(=C–H) 3064, ν(C=C) 1428, ν(C–N) 1334, δ(C–H Ph) 747 cm⁻¹.

Synthesis of the phosphine gold chlorido precursors.
Gold chloride triphenylene phosphane ([AuCl(P1)]). [AuCl(tht)] (0.078 g, 0.24 mmol) was added to a previously prepared solution of P1 (0.100 g, 0.24 mmol) in dichloromethane (5 mL). The mixture was stirred for 1 h. The product was precipitated by the addition of hexane (10 mL). The obtained white solid was filtered and dried in vacuo. Yield 91%. ¹HNMR (400 MHz, CDCl₃, ppm): δ 8.86 (dd, J = 15.3, 1.7 Hz, 1H, H₁), 8.73 (dd, J = 8.5, 2.5 Hz, 1H), 8.70–8.63 (m, 3H), 8.40–8.37 (m, 1H), 7.77–7.49 (m, 15H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 33.54. IR (, cm⁻¹): ν(=C–H) 3052, ν(C=C) 1475–1448, δ(C–H Ph) 760–693 cm⁻¹.
Gold chloride phenanthrene phosphane ([AuCl(P2)]). The synthesis of [AuCl(P2)] was performed by following the same procedure as [AuCl(P1)] by substitution of P1 for P2 (0.100 g, 0.28 mmol). Yield 82%. ¹H-NMR (400 MHz, CDCl₃, ppm): δ 8.78–8.75 (m, 1H, H₆), 8.71 (d, J = 8.6 Hz, 1H, H₅), 8.47 (m, 1H, H₉), 7.79–7.72 (m, 1H), 7.71–7.62 (m, 6H), 7.61–7.56 (m, 3H), 7.55–7.47 (m, 5H), 7.30 (d, J = 15.6 Hz, 1H, H₁). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 27.22. IR (, cm⁻¹): ν(=C–H) 3052, ν(C=C) 1435, δ(C–H Ph) 740 cm⁻¹.
Gold chloride carbazole phosphane ([AuCl(P3)]). The synthesis of [AuCl(P3)] was performed by following the same procedure as [AuCl(P1)] by substitution of P1 for P3 (0.100 g, 0.23 mmol). Yield 96%. ¹H-NMR (400 MHz, CDCl₃, ppm): δ 8.08–8.04 (m, 4H, H₄), 8.00–7.93 (m, 2H, o-Ph), 7.83–7.77 (m, 1H, p-Ph), 7.66–7.60 (m, 2H, m-Ph), 7.33 (ddd, J = 7.9, 7.2, 1.0 Hz, 4H, H₃), 7.26 (d, J = 8.4 Hz, 4H, H₁), 7.18 (ddd, J = 8.4, 7.2, 1.3 Hz, 4H, H₂). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 72.5. ¹³C{¹H} NMR (100 MHz, CDCl₃, ppm): δ 141.2 (d, J = 4 Hz, C₆), 135.0 (d, J = 3 Hz, p-Ph), 133.8 (d, J = 19 Hz, o-Ph), 130.3 (d, J = 14 Hz, m-Ph), 128.9 (d, J = 76 Hz, ipso-Ph), 127.2 (s, C₂), 127.1 (C₅), 123.4 (C₃), 120.6 (C₄), 113.8 (d, J = 6.5 Hz, C₁). IR (, cm⁻¹): ν(=C–H) 3052, ν(C=C) 1428, ν(C–N) 1334, δ(C–H Ph) 740 cm⁻¹.

Synthesis of the complexes.
(1a). Compound 1a was synthesized according to the literature method.³Part A. Synthesis of 4,4,5,5-Tetramethyl-2-(triphenylen-2-yl)-1,3,2-dioxaborolane (TPBpin). The synthesis of TPBpin was carried out according to the literature.¹⁸ 2-bromotriphenylene (0.300 g, 0.98 mmol), bis(pinacolato) diborate (0.372 g, 1.46 mmol), [1,10 bis(diphenylphosphino)ferrocene] dichloropalladium(II) (0.0294 g, 0.04 mmol), and potassium acetate (0.243 g, 2.96 mmol) were dissolved in anhydrous 1,4-dioxane (20 ml) and refluxed under nitrogen for 24 h. The reaction mixture was diluted with ethyl acetate and washed with brine and water (2 × 10 mL). Then, the organic layer was extracted and dried over anhydrous MgSO₄. After evaporation of the solvent, the crude product was purified by column chromatography on silica gel using a dichloromethane/hexane (1 : 1) mixed eluent. A pale-yellow powder product was obtained after purification Yield 13%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 9.14 (s, 1H), 8.82 (m, 1H), 8.67 (m, 4H), 8.06 (dd, J = 8.2, 1.2 Hz, 1H), 7.67 (m, 4H), 1.43 (s, 12H). IR (, cm⁻¹): ν(C–H) 2974, δ(C–H) 1804, ν(B–O) 1362, δ(C–H Ph) 751–682 cm⁻¹. Part B. Cs₂CO₃ (0.032 g, 0.10 mmol) and TPBpin (0.029 g, 0.08 mmol) were suspended in isopropyl alcohol (10 mL) and [AuCl(PPh₃)] (0.032, 0.06 mmol) was added to the suspension. After 5 days stirring at RT in the dark, the solvent was evaporated in vacuo and the residue was extracted with dichloromethane (2 × 10 mL). The obtained solution was filtered through Celite then the solvent was removed, and a white solid powder was obtained. Yield 88%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.94 (d, J = 6.0 Hz, 1H, H₁*), 8.82–8.78 (m, 1H), 8.69–8.61 (m, 3H), 8.56 (dd, J = 8.2, 1.6 Hz, 1H, H₃*), 7.92 (ddd, J = 8.0, 4.9, 0.9 Hz, 1H, H₂*), 7.70–7.64 (m, 6H), 7.64–7.57 (m, 4H), 7.56–7.48 (m, 9H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 43.25. ES-MS (+) m/z: 709.1292 ([M + Na]⁺, calcd 709.1335), 1145.2009 ([2 M − L]⁺, calcd 1145.2015). IR (, cm⁻¹): ν(=C–H) 3044, ν(C=C) 1435, δ(C–H Ph) 750–693 cm⁻¹.
(2a). The synthesis of 2a was performed by following the same procedure as 1a: Cs₂CO₃ (0.176 g, 0.54 mmol), 9-phenanthracenylboronic acid (0.100 g, 0.45 mmol) and [AuCl(PPh₃)] (0.178, 0.36 mmol). Yield 74%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.74–8.71 (m, 1H, H₆*), 8.70–8.67 (m, 1H, H₉*), 8.66–8.63 (m, 1H, H₅*), 8.00 (d, J = 6.5 Hz, 1H, H₁*), 7.85–7.79 (m, 1H, H₂*), 7.73–7.65 (m, 6H, Ph), 7.59–7.48 (m, 13H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 44.26. ES-MS (+) m/z: 637.1360 ([M + H]⁺, calcd 637.1359), 659.1177 ([M + Na]⁺, calcd 659.1179). IR (, cm⁻¹): ν(=C–H) 3044, ν(C=C) 1435, δ(C–H Ph) 740–687 cm⁻¹.
(3a). A solution of carbazole (0.027 g, 0.16 mmol) in dichloromethane (5 mL) was added to a solution of KOH (0.027 g, 0.48 mmol) in methanol (2 mL). The reaction mixture was stirred for 30 min at RT. Then a solution of [AuCl(PPh₃)] (0.079 g, 0.16 mmol) in dichloromethane was added. After 1 h stirring the solvent was evaporated in vacuo and the remaining solid was dissolved in dichloromethane (5 mL) and filtered through Celite. The solvent was removed, and the white solid was recrystallized with dichloromethane/hexane to obtain the pure product. Yield 89%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.14 (m, 2H, H₄*), 7.77 (dd, J = 8.0, 0.8 Hz, 2H, H₁*), 7.70–7.63 (m, 6H Ph), 7.59–7.51 (m, 9H, Ph), 7.34 (ddd, J = 8.2, 7.0, 1.3 Hz, 2H, H₂*), 7.09 (ddd, J = 7.9, 7.0, 1.0 Hz, 2H, H₃*). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 33.71. ¹³C{¹H} NMR (100 MHz, CDCl₃, ppm): δ 149.3 (s, C₆*), 134.4 (d, J = 13.6 Hz, o-Ph), 132.1 (d, J = 2.6 Hz, p-Ph), 129.5 (d, J = 11.6 Hz, m-Ph), 129.3 (d, J = 60 Hz, ipso-Ph), 124.2 (d, J = 2.5 Hz, C₅*), 124.1 (C₂*), 120.0 (C₄*), 116.8 (C₃*), 113.5 (C₁*). MALDI-TOF(+) m/z: 625.1 ([M]⁺, calcd 625.1234). IR (, cm⁻¹): ν(=C–H) 3064, ν(C=C) 1441, ν(C–N) 1235, δ(C–H Ph) 747–687 cm⁻¹.
(1b). Cs₂CO₃ (0.114 g, 0.35 mmol) and phenylboronic acid (0.036 g, 0.29 mmol) were suspended in isopropyl alcohol (10 mL) and a solution of [AuCl(P1)] (0.050 g, 0.08 mmol) in dichloromethane (5 mL) was added to the suspension. After 2 days stirring at 40 °C the precipitated product was filtered and dried in vacuo. Next, the solid was dissolved in dichloromethane (5 mL) and filtered through Celite. The solvent was removed, and a white solid powder was obtained. Yield 18%. ¹H NMR (400 MHz, CDCl₃, ppm): δ 8.98 (dd, J = 13.7, 1.7 Hz, 1H, H₁), 8.75–8.70 (dd, J = 8.5, 2.2 Hz, 1H, H₃), 8.69–8.63 (m, 3H), 8.45–8.40 (m, 1H), 7.81–7.75 (m, 1H, H₂), 7.73–7.60 (m, 10H), 7.57–7.47 (m, 6H), 7.35–7.30 (m, 2H, Ph–Au H₁₅ or H₁₆), 7.15–7.09 (m, 1H, Ph–Au H₁₇). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 43.98. ES-MS (+) m/z: 1395.2715 ([2 M + Na]⁺, calcd 1395.2773), 1295.2443 ([2 M − Ph]⁺, calcd 1295.2484). IR (, cm⁻¹): ν(=C–H) 3058, ν(C=C) 1635–1435, δ(C–H Ph) 820–687 cm⁻¹.
(2b). The synthesis of 2b was performed by following a similar procedure as 1b: Cs₂CO₃ (0.020 g, 0.06 mmol), phenylboronic acid (0.01 g, 0.05 mmol) and [AuCl(P2)] (0.02 g, 0.04 mmol). In this synthesis the reaction mixture was stirred for 5 days at RT. Yield 63%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.79–8.68 (m, 3H, H₅, H₆, H₉), 7.78–7.66 (m, 6H), 7.63 (dd, J = 7.9, 1.5 Hz, 1H), 7.60–7.45 (m, 10H), 7.30 (d, J = 13.3 Hz, 1H, H₁), 7.26–7.23 (m, 2H), 7.11–7.04 (m, 1H, p-PhAu). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 39.53. ES-MS (+) m/z: 659.1161 ([M + Na]⁺, calcd 659.1179), 1195.2159 ([2 M − Ph]⁺, calcd 1195.2171). IR (, cm⁻¹): ν(=C–H) 3052, ν(C=C) 1435, δ(C–H Ph) 753–687 cm⁻¹.
(3b). The synthesis of 3b was performed by following the same procedure as 2b: Cs₂CO₃ (0.014 g, 0.04 mmol), phenylboronic acid (0.004 g, 0.04 mmol) and [AuCl(P3)] (0.020 g, 0.03 mmol). Yield 38%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.05 (d, J = 6.7 Hz, 4H, H₄), 8.01 (m, 2H, o-Ph), 7.73 (m, 1H, p-Ph), 7.62–7.56 (m, 2H, m-Ph), 7.53 (d, J = 8.5 Hz, 4H, H₁), 7.43–7.39 (m, 2H, o-PhAu), 7.33–7.28 (m, 4H, H₃), 7.24–7.16 (m, 6H, H₂, m-PhAu), 7.09–7.04 (m, 1H, p-PhAu). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 100.79. ES-MS (+) m/z: 737.1381 ([M + Na]⁺, calcd 737.1397), 1351.2601 ([2 M − Ph]⁺, calcd 1351.2607). IR (, cm⁻¹): ν(=C–H) 3058, ν(C=C) 1435, ν(C–N) 1201, δ(C–H Ph) 740 cm⁻¹.
(1c). Cs₂CO₃ (0.040 g, 0.12 mmol) and P1 (0.035 g, 0.10 mmol) were suspended in isopropyl alcohol (10 mL) and a solution of [AuCl(P1)] (0.026 g, 0.04 mmol) in dichloromethane (5 mL) was added to the suspension. After 5 days stirring at RT the precipitated product was filtered and dried in vacuo. Next, the solid was dissolved in dichloromethane (5 mL) and filtered through Celite. The solvent was evaporated in vacuo and the residue was washed with methanol (2 × 5 mL). The solvent was removed, and an orange solid powder was obtained. Yield 16%. ¹H NMR (400 MHz, CDCl₃, ppm): δ 9.07 (dd, J = 13.9, 1.7 Hz, 1H, H₁), 9.01 (d, J = 6.0 Hz, 1H, H₁*), 8.86–8.81 (m, 1H), 8.77 (dd, J = 8.6, 2.2 Hz, 1H, H₃), 8.71–8.62 (m, 6H), 8.60 (dd, J = 8.2, 1.6 Hz, 1H, H₃*), 8.51–8.47 (m, 1H), 7.98 (ddd, J = 8.0, 4.9, 0.8 Hz, 1H, H₂*), 7.84 (ddd, J = 10.2, 8.5, 1.6 Hz, 1H, H₂), 7.81–7.50 (m, 18H). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 44.00. MALDI-TOF(+) m/z: 859.1785 ([M + Na]⁺, calcd 859.1805), 413.1457 ([M − Au − L]⁺, calcd 412.1381). IR (, cm⁻¹): ν(=C–H) 2962, ν(C=C) 1433, δ(C–H Ph) 792–690 cm⁻¹.
(2c). The synthesis of 2c was performed by following a similar procedure as 1c: Cs₂CO₃ (0.062 g, 0.19 mmol), 9-Phenanthracenylboronic acid (0.034 g, 0.16 mmol) and [AuCl(P2)] (0.050, 0.08 mmol). Yield 12%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.90 (d, J = 8.2 Hz, 1H), 8.80 (d, J = 8.5 Hz, 1H), 8.74 (d, J = 8.4 Hz, 1H), 8.69 (d, J = 7.9 Hz, 1H), 8.64–8.57 (m, 2H), 7.95 (d, J = 6.4 Hz, 1H, H₁*), 7.85–7.71 (m, 7H), 7.67–7.44 (m, 13H), 7.36 (d, J = 13.6 Hz, 1H, H₁). ³¹P{¹H} NMR (162 MHz, CDCl₃, ppm): δ 40.67. MALDI-TOF(+) m/z: 737.1662 ([M + H]⁺, calcd 737.1672), 759.1483 ([M + Na]⁺, calcd 759.1492). IR (, cm⁻¹): ν(=C–H) 3053, ν(C=C) 1434, δ(C–H Ph) 741–691 cm⁻¹.
(3c). Carbazole (0.013 g, 0.08 mmol) and [AuCl(P3)] (0.050 g, 0.07 mmol) were added to a solution of K₂CO₃ (0.031 g, 0.22 mmol) in acetone (0.5 mL). The reaction mixture was stirred for 24 h at RT. Then the solvent was evaporated in vacuo and the remaining solid was recrystallized with dichloromethane/hexane to obtain the yellow pure product. Yield 33%. ¹H NMR (500 MHz, CDCl₃, ppm): δ 8.13–8.02 (m, 8H, H₄, H₄*, o-Ph), 7.87–7.81 (m, 1H, p-Ph), 7.72–7.66 (m, 2H, m-Ph), 7.48 (d, J = 8.4 Hz, 4H, H₁), 7.46–7.41 (m, 2H, H₁*), 7.37 (pt, J = 7.5 Hz, 3H, H₃), 7.26–7.21 (m, 6H, H₂, H₂*), 7.06 (pt, 7.4 Hz, 2H, H₃*). ³¹P{¹H} NMR (202 MHz, CDCl₃, ppm): δ 79.16. ¹³C{¹H} NMR (125 MHz, CDCl₃, ppm): δ 149.0 (s, C₆*), 141.5 (d, J = 4.5 Hz, C₆), 134.9 (p-Ph), 133.8 (d, J = 19 Hz, o-Ph), 130.5 (d, J = 13.5 Hz, m-Ph), 129.2 (d, J = 73 Hz, ipso-Ph), 127.3 (C₅), 127.2 (C₂), 124.2 (C₂*), 123.5 (C₃), 120.7 (C₄), 119.9 (C₄*), 117.0 (C₃*), 113.9 (d, J = 6.2 Hz, C₁), 113.3 (C₁*). MALDI-TOF(+) m/z: 804.1511 ([M + H]⁺, calcd 804.1837), 1077.1874 ([Au(P3)₂]⁺, calcd 1078.2622). IR (, cm⁻¹): ν(=C–H) 2961, ν(C=C) 1450, ν(C–N) 1195, δ(C–H Ph) 743–694 cm⁻¹.

Data availability

The datasets supporting this article, including experimental data, computational files, and characterization data, are available in the ESI.† Additional data are available from the corresponding author upon reasonable request.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

The authors are grateful to Projects PID2020-115637GB-I00, PID2022-139296NB-I00 and PID2023-148453NB-I00 funded by the Ministerio de Ciencia, Innovación y Universidades of Spain MCIU/AEI/10.13039/501100011033 and FEDER, UE. This article is based upon work from COST Action CA22131, LUCES Supramolecular LUminescent Chemosensors for Environmental Security, supported by COST (European Cooperation in Science and Technology). Also acknowledges IFARHU-SENACYT program in Panamá for the grant no. 270-2022-112 as Ph.D. Scholarship.

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Footnote

† Electronic supplementary information (ESI) available. CCDC 2409503–2409506. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d4qi03225j

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