Synthesis and photochromic modulation of aromaticity in dinaphthylethene derivatives

Abstract

Photoinduced modulation of aromaticity, intricately coupled with the reversible photoisomerization of diarylethenes, establishes a fundamental mechanism for tailoring photoreactivity and developing multifunctional optical materials. In this study, we present the synthesis and comprehensive photochemical characterization of dinaphthylethene derivatives 1o–4o functionalized with naphthalene side chains. Experimental results reveal that specific light irradiation enables precise modulation of both (i) the photochromic reactivity of 1o–4o and (ii) the aromaticity of their naphthalene substituents. To unravel the mechanistic link between photocyclization and aromaticity dynamics, we conducted nucleus-independent chemical shift (NICS) calculations and chemical bond character analyses of the naphthalene units. These theoretical insights, combined with experimental observations of photochromic reactivity, fluorescence intensity variations and rapid thermal back-reaction kinetics, establish a robust structure–function correlation: (i) light-driven cyclization selectively alters the electron delocalization in specific naphthalene rings; (ii) emission quenching correlates with closed isomer formation, enabling real-time monitoring of photostationary states; (iii) large activation energy barriers facilitate rapid thermal reversion, critical for reversible applications. Collectively, this work provides a strategic framework for designing photoresponsive diarylethenes capable of dynamically tuning both six-membered aromatic systems and optoelectronic properties. The synergistic integration of photoswitching, fluorescence modulation, and thermal stability positions these materials as promising candidates for next-generation photonic devices, including adaptive optoelectronics and erasable optical memory systems.

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1. Introduction

Photochromism describes the light-driven reversible interconversion between two isomeric states of a chemical species, which may occur unidirectionally or bidirectionally.¹ This process manifests as distinct photophysical properties between isomers, including pronounced differences in coloration, absorption spectra, and other optoelectronic characteristics.² Over decades of research, several prototypical photochromic systems have emerged, including diarylethenes,^3,4 fulgides,⁵ spiropyrans,^6,7 azobenzenes,^8,9 and donor–acceptor Stenhouse adducts (DASAs),^10,11 each demonstrating unique switching mechanisms.

Diarylethene derivatives, characterized by a hexatriene skeleton formed through three interconnected aromatic rings, undergo UV-light induced photocyclization to yield closed-ring cyclohexadiene structures.^12,13 These compounds have attracted considerable attention for optoelectronic applications (e.g., molecular memories, optical switches, nanoactuators)^14,15 due to their synthetic accessibility, exceptional thermal stability of both open and closed isomers, fatigue resistance over repeated cycling and high photoreactivity across solution and crystalline phases.^14,15 Conventional diarylethene design employs weakly aromatic five-membered heterocycles (thiophene, thiazole, furan, pyrrole derivatives) as side chains. In contrast, six-membered aromatic systems, particularly naphthalene, remain underexplored as side-chain components despite their potential aromaticity modulation capabilities.^16,17

Aromaticity, a cornerstone concept in physicochemical molecular design,^18,19 presents both challenges and opportunities when engineering photochromic diarylethenes. While photoinduced isomerization offers a pathway to modulate six-membered ring aromaticity, inherent π-electron delocalization and aromatic stabilization energies in open isomers often suppress photocyclization efficiency when six-membered aromatics are incorporated as ethene bridges or side chains.^20–23

To address this dichotomy, we designed four novel diarylethene derivatives (1o–4o) featuring naphthalene side units. Through systematic investigation of their photochromic behavior, aromaticity dynamics via theoretical NICS calculations, and fluorescence modulation, we demonstrate that strategic positioning of naphthalene moieties preserves photocyclization capability while enabling aromaticity control. These findings establish design principles for next-generation photoresponsive materials with programmable optoelectronic properties.

2. Results and discussion

2.1. Synthetic procedures

Four target photochromic diarylethene derivatives (1o–4o), featuring naphthalene side chains, were successfully synthesized following the pathway outlined in Scheme 1 and Scheme S1. Key intermediates, including 2,3-dibromobenzo[b]thiophene (S1),²⁴ 4,4,5,5-tetramethyl-2-(3-methyl-naphthalen-2-yl)-1,3,2-dioxaborolane (S3)^25–27 and 4,5-dibromo-2-phenylthiazole (S2),²⁸ were prepared according to established literature procedures. Additionally, 4,4,5,5-tetramethyl-2-(1-methyl-naphthalen-2-yl)-1,3,2-dioxaborolane (S4) could be unambiguously obtained following the reported literature procedures.^27,29,30 And then the originally designed dinaphthylethene derivatives 2o′ and 4o′ were subsequently prepared via Suzuki–Miyamura coupling reactions (Scheme S1). However, bromination predominantly yielded 1-bromo-4-methylnaphthalene as the major product, likely due to the higher reactivity of the para-position relative to the methyl group in 1-methylnaphthalene, which directed the preferential occurrence of bromination at this site. The final dinaphthylethene compounds 1o–4o were then efficiently synthesized using a standardized Pd(0)-catalyzed Suzuki–Miyamura cross-coupling protocol, highlighting the versatility of this methodology for constructing naphthalene-functionalized photochromic systems. Detailed synthetic procedures and characterization data are provided in the SI.

Scheme 1 The synthetic route of dinaphthylethene derivatives 1o–4o (A, B, C, and D denote rings A, ring B, ring C, and ring D; a–j and a′–j′ denote the carbon–carbon bond).

2.2. Geometry analysis

The photocyclization capability of diarylethene photoswitches, governed by the Woodward–Hoffmann rules, is determined by their molecular geometries. The 6π-conrotatory photocyclization reaction in diarylethene compounds occurs exclusively when the molecules adopt an antiparallel conformation, with the reactive carbon atoms separated by less than 0.4 nm.³¹ To elucidate the conformational preferences of compounds 1o–4o, density functional theory (DFT) calculations and nuclear magnetic resonance (NMR) spectroscopy were employed.

DFT calculations were performed using the B3LYP functional with the 6-31+G(d,p) basis set in Gaussian 16 (visualized via Gaussian View 6.1) (Fig. 1). The optimized geometries revealed that compounds 1o, 2o, and 4o predominantly adopt photoreactive antiparallel conformations, characterized by oppositely oriented methyl groups on the reactive carbons. Critically, the distance between these reactive carbons (<0.4 nm) confirms the photocyclization capability of 4o under specific irradiation. Additionally, compounds 2o and 4o exhibit non-covalent heteroatomic interactions (e.g., S5–H40: 0.294 nm in 2o; S5–H38: 0.292 nm and N3–H51: 0.248 nm in 4o) that maintain antiparallel conformations while preserving sub-0.4 nm and less-0.4 nm reactive carbon distances. While for compound 3o, additional stabilizing interactions (N3–H38: 0.256 nm) stabilize the photoinert parallel conformations, where both methyl groups align on the same molecular plane.

Fig. 1 The optimized structures and activation energies of open and closed isomers of 1o–4o by DFT calculations (B3LYP/6-31+G(d,p)).

DFT results further indicate low energy barriers (Table 1) between parallel and antiparallel conformations of all compounds 1o–4o, enabling free interconversion at ambient temperature. This dynamic equilibrium allows photocyclization-competent antiparallel conformers to regenerate from photoinactive parallel states in solution. Moreover, the relative stability of open isomers (2o and 4o) compared to the closed isomers (2c and 4c) may make 2o and 4o exhibit excellent photochromic reactivity, rather than undergo dehydrogenation to generate 2f and 4f. This part will be discussed later.

Table 1 The free energy of optimized structures of 1–4 by DFT calculations (B3LYP/6-31+G(d,p))

Isomer & conformation		1 (kcal mol^−1)	2 (kcal mol^−1)	3 (kcal mol^−1)	4 (kcal mol^−1)
Open isomer	Antiparallel conformation	0	0	0	0
	Parallel conformation	0.1751	0.9180	−1.9177	0.0885
Closed isomer		74.4083	40.3796	69.4666	34.4867
Fused compounds		—	9.1748	—	1.2080

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Complementary NMR studies using a Bruker Avance NEO 400 MHz spectrometer in CDCl₃ corroborated these findings. The unsymmetrical structures of 1o–4o were confirmed by distinct methyl group signals in their ¹H and ¹³C NMR spectra (for details, see Section S2 in the SI), consistent with the presence of a single dominant conformation (either parallel or antiparallel) for each open isomer in solution. This conformational uniformity simplifies the interpretation of UV-Vis absorption spectra and photoreactivity analysis under light irradiation.

2.3. Evaluation of aromaticity

The aromaticity of the naphthalene side chains was evaluated using nucleus-independent chemical shifts (NICS), a computational method that quantifies the magnetic criterion of aromaticity. NICS(1)zz values were calculated 1 Å above the geometric center of each benzenoid ring. Negative values denote diatropic ring currents (aromaticity), positive values indicate paratropic currents (antiaromaticity), and values near zero correspond to nonaromatic systems. The magnitude of negativity directly correlates with aromatic strength.

All NICS(1)zz calculations were performed at the B3LYP/6-31+G(d,p) level of theory. As shown in Fig. 2 and Table S1, open isomers 1o–4o exhibit negative NICS(1)zz values across all naphthalene rings, confirming their aromatic character. Subtle variations in aromaticity arise from structural differences in the ethene bridges (benzo[b]thiophene vs. phenylthiazole) and substituent positioning.

Fig. 2 NICS values for rings A–D of (a) 1, (b) 2, (c) 3, and (d) 4 calculated 1.0 Å above the geometric ring centers.

Photoinduced cyclization to closed isomers 1c–4c (Fig. 3 and Table S1) significantly alters the aromatic landscape (Fig. 2 and Table S1). Cyclization converts aromatic rings A/B to antiaromatic (positive NICS(1)zz) and rings C/D to nonaromatic (near-zero values) for compounds 1 and 3, resulting in complete loss of diatropic currents. This dual effect may suppress 6π-electrocyclization reactivity or accelerate thermal back-reversion to open isomers in both solution and solid states. Cyclization selectively reduces aromaticity in ethene-proximal rings A/B (transitioning to nonaromatic) for compounds 2 and 4, while distal rings C/D retain aromatic character (negative NICS(1)zz). This partial aromatic preservation enables conventional photocyclization kinetics with relative stable thermal reversion.

Fig. 3 Photochromic reaction schemes of dinaphthylethene derivatives 1o–4o upon light irradiation.

The calculated NICS profiles (Fig. 2 and Table S1) demonstrate that photocyclization dynamically modulates side-chain aromaticity, which reciprocally governs photocyclization capability. To validate this structure–function relationship, we systematically investigated the photochemical behavior of derivatives 1o–4o across different solvents, which will be discussed later.

2.4. X-ray crystal analysis and bond characters

Single crystals of compounds 1o–4o suitable for X-ray diffraction were successfully obtained by slow solvent evaporation of a hexane/dichloromethane mixture. All molecular structures were unambiguously determined through X-ray crystallographic analysis, as shown in Fig. 4 (for details, see Section S5 in the SI).

Fig. 4 Single crystal X-ray diffraction structures of dinaphthylethene derivatives (a) 1o, (b) 2o, (c) 3o and (d) 4o, where nitrogen and sulfur atoms are highlighted in blue and yellow, respectively.

In their crystal structures, the unit cells of compounds 1o and 3o contain multiple independent molecules, whereas those of 2o and 4o contain only one. Additionally, compounds 1o–3o adopt a parallel conformation, characterized by their two naphthalene rings being oriented parallel to each other and the methyl groups or hydrogen atoms on the reactive carbons pointing uniformly within each molecule. For 3o in particular, the stable, photo-nonreactive parallel conformations are stabilized by expected intramolecular non-covalent heteroatomic interactions (N–H: 0.2439 nm and 0.2678 nm; S–H: 0.3028 nm and 0.2904 nm), which suppress photo-induced cyclization reactions in the crystalline state. In contrast, compound 4o crystallizes in an antiparallel conformation. Here, intramolecular non-covalent N–H and S–H interactions between N/S atoms on the central phenyl thiazole ethene bridge and H atoms on the naphthalene side chains are inferred from the close atomic contacts (N–H: 0.2701 nm; S–H: 0.2778 nm) observed in its crystal structure. However, the distance between the reactive carbons on the naphthalene side units exceeds 0.4 nm (specifically 0.4136 nm), indicating that 4o exhibits no photochromism in the crystalline state upon light irradiation.

Therefore, no photo-induced isomerization occurs for any of these four compounds in the crystal state.

Another prerequisite for diarylethene compounds to undergo photoinduced isomerization reactions is the presence of a typical hexatriene structure.¹² Specifically, the bond connecting the ethene bridge and methyl group must exhibit double-bond character. This characteristic is also the basis for the term ‘diarylethene’, which reflects its structural features. Therefore, the nature of the carbon–carbon bonds in the side chains was elucidated using X-ray crystal analysis and DFT calculations.

X-ray crystal analysis of naphthalene reveals alternating shorter and longer C–C bonds, demonstrating a partial single-double bond alternating character that challenges simple resonance models (Fig. S17).³² This characteristic suggests that different connecting position of the ethene bridge to the naphthalene unit may lead to distinct photochromic properties in dinaphthylethene derivatives. Specifically, dinaphthylethene derivatives with the ethene bridge and methyl group connected to both α positions, such as compounds 2o and 4o, may adopt a hexatriene structure and undergo photoinduced isomerization. In contrast, derivatives with the ethene bridge and methyl group connected to both β positions, such as compounds 1o and 3o, lack the structure of hexatriene and exhibit non-photoreactivity.

The bond characteristics of the naphthalene units in dinaphthylethene derivatives 1o–4o were calculated by both DFT calculations. As shown in Table 2, the carbon–carbon bonds (a and a′) in the naphthalene units of 1o and 3o that connects to the ethene bridge and methyl group exhibit relatively longer distances compared to adjacent carbon–carbon bonds, indicating single bond character. This structural feature likely explains why compounds 1o and 3o lack the characteristic structural properties of diarylethenes and, consequently, may not exhibit photochromic reactivity.

Table 2 The carbon–carbon bond length of naphthalene side chains in 1o–4o from DFT calculations (B3LYP/6-31G+(d,p))

	1o	2o	3o	4o
a/a′	1.43698/1.43605	1.38354/1.38244	1.43814/1.43500	1.38453/1.38237
b/b′	1.38533/1.38419	1.43840/1.43529	1.38604/1.38449	1.43818/1.43762
c/c′	1.41713/1.41835	1.42323/1.42241	1.41645/1.41603	1.42164/1.42326
d/d′	1.42086/1.42081	1.37863/1.37809	1.42108/1.42137	1.37829/1.37891
e/e′	1.37632/1.37649	1.41316/1.41373	1.37622/1.37609	1.41327/1.41325
f/f′	1.41708/1.41701	1.37860/1.37887	1.41717/1.41751	1.37871/1.37872
g/g′	1.37668/1.37667	1.42360/1.42376	1.37669/1.37645	1.42360/1.42361
h/h′	1.42057/1.42073	1.43437/1.43420	1.42050/1.42099	1.43457/1.43470
i/i′	1.41838/1.41849	1.38057/1.38088	1.41835/1.41755	1.38100/1.38027
j/j′	1.38028/1.38056	1.41156/1.4135	1.38036/1.38150	1.41176/1.41193
k/k′	1.42958/1.42964	1.43870/1.43876	1.42977/1.43009	1.43850/1.43855

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However, for compounds 2o and 4o, the ethene bridge and reactive carbon are connected to the α and β positions of the naphthalene units, respectively. This configuration results in shorter bond distances (a and a′) compared to neighbouring carbon–carbon bonds, indicating pronounced double bond character. The presence of such conjugation confers the characteristic structural features of diarylethenes to 2o and 4o, thereby enabling potentially photochromic isomerization reactions upon light irradiation.

Therefore, the bond character of the naphthalene unit plays a pivotal role in governing the structural integrity of diarylethenes and dictating their photochromic behavior. This property directly modulates their capacity to undergo reversible photoisomerization upon light irradiation.

2.5. Optical properties

In order to corroborate the theoretical results and X-ray crystal analysis described above, the optical properties of dinaphthylethene derivatives 1o–4o were systematically investigated under controlled light irradiation in various solutions. Consistent with the discussion above, compounds 1o and 3o exhibited no photochromic reactivity in either polar or nonpolar media; however, prolonged UV light irradiation induced gradual decomposition (Fig. S19 and S20 in the SI). In contrast, derivatives 2o and 4o displayed characteristic photochromic behavior, showing well-defined absorption spectral changes upon light irradiation that are consistent with conventional diarylethene photoswitches (Fig. 5 and Fig. S20, S21 in the SI).

Fig. 5 (a) and (b) Photochromic reaction schemes of dinaphthylethene derivatives 2o and 4o upon light irradiation. (c) and (d) UV-vis absorption spectral changes of 2o and 4o in n-hexane upon UV and visible light irradiation.

The UV-Vis absorption spectra of compounds 2o and 4o exhibited distinct spectral changes upon UV light irradiation. These changes included a gradual decrease in absorption at 292 nm and 302 nm, concomitant with the emergence of new absorption bands in the 400–550 nm wavelength range. The presence of two isosbestic points at about 284 nm and 305 nm demonstrates the photoinduced interconversion between the open isomers (2o, 4o) to closed isomers (2c, 4c). The modest spectral changes for 2o and 4o in the visible region (400–520 nm) upon UV light irradiation in polar solvents likely arise from a twisted intramolecular charge transfer (TICT) effect,³³ which stabilizes the parallel conformation of these compounds in polar solvents (Fig. S21 and S22 in the SI). Photocycloreversion reactions were subsequently induced by irradiating the closed isomers 2c and 4c with visible light (>450 nm). Experimental results confirm that compounds 2o and 4o, with preserved partial aromaticity in closed states, exhibit superior photochromic performance in solution. Moreover, no photochromic behavior was observed for compounds 2o and 4o in PMMA films (Fig. S23). Along with X-ray crystallographic analysis, this result indicates that the non-photoreactive parallel conformations of compounds 2o and 4o exist in both the solid state and in their crystalline forms.

As the UV-Vis absorption intensity of compound 2o is relatively higher than that of compound 4o in the visible light region (400–550 nm), it was selected to evaluate reversible photochromic switching under alternating UV and visible light irradiation cycles (Fig. S24). Repeated and prolonged irradiation resulted in minimal degradation and byproduct formation. This stability exceeds that observed in diarylethene photoswitches containing six-membered aromatic rings within the ethene bridge or as side-chain substituents, highlighting their suitability for molecular switching applications.²⁰ Based on previous research experience,³⁴ the closed-ring isomers of photochromic diarylethenes bearing hydrogen atoms at their reactive carbons may undergo oxidation by oxygen via hydrogen abstraction, potentially forming fused products. However, compounds 2 and 4 exhibit high fatigue resistance, indicating that ring-opening process (cycloreversion reaction) is strongly favored over oxidative fusion. This kinetic preference arises because the thermal activation barrier for cycloreversion (ring-opening) is substantially higher than that for dehydrogenation (Fig. 1 and Table 1: 40.3796 kcal mol⁻¹vs. 31.2048 kcal mol⁻¹ for 2; 34.4867 kcal mol⁻¹vs. 33.2787 kcal mol⁻¹ for 4). This energy difference kinetically traps molecules in the closed-ring form, favoring ring-opening reactions over dehydrogenation.

The photocyclization quantum yields of dinaphthylethylene derivatives 2o and 4o in n-hexane solution were determined to be 56% and 62%, respectively. These values are significantly higher than those typically reported for conventional aromatic diarylethene systems. This enhancement may be attributed to the intramolecular non-covalent heteroatomic interactions between the benzo[b]thiophene/phenyl thiazole ethene bridges and naphthalene side units. This interaction effectively stabilizes the antiparallel conformation, a prerequisite for efficient photocyclization.

By integrating theoretical analysis (NICS(1)zz calculations and bond character assessments of naphthalene side chains) with experimental investigations of photochromic behavior, we established that the combined effects of aromaticity modulation in benzenoid rings and single-bond character of the C–C linkage suppress the photoreactivity in compounds 1o and 3o. Conversely, in derivatives 2o and 4o, the localized aromaticity changes within the benzenoid ring directly bonded to the ethene bridge/methyl group, coupled with pronounced double-bond character of the C–C linkage, enable efficient photoinduced cyclization reaction. These findings demonstrate that two critical factors govern diarylethene photoreactivity: (i) the electronic nature of the connecting C–C bond, and (ii) the spatially controlled aromaticity modulation in specific benzenoid rings.

Diarylethene compounds exhibiting dual photochromic-fluorescent switching capabilities represent a highly desirable objective for advanced applications in fluorescence-based optical memory systems, biomolecular tracking probes, and super-resolution microscopy.^35,36 Significantly, the strategic incorporation of naphthalene moieties into compounds 1o–4o confers blue fluorescence emission to their open isomers across various solvents (for details, see Section S7 in the SI). The fluorescence quantum yields of compounds 1o–4o in n-hexane were determined to be 4.11%, 4.21%, 3.51%, and 2.33%, respectively (Fig. S28). The fluorescence modulation of 2o and 4o was quantitatively tracked during photocyclization processes, leveraging the linear correlation between fluorescence intensity and open isomer concentration. In n-hexane solution, compound 2o displayed a fluorescence emission maximum at 412 nm (λ_ex = 292 nm), while compound 4o exhibited a fluorescence emission maximum at 430 nm (λ_ex = 301 nm). Both compounds demonstrated progressive fluorescence quenching upon UV-induced formation of their closed isomers (2c and 4c) (Fig. 6 and Fig. S27), with analogous solvent-independent behavior observed across tested media. These systematic investigations establish 2o and 4o as prototypical photoswitchable “turn-off” fluorescent systems in solution-phase applications.

Fig. 6 The normalized fluorescence spectra of (a) 2o and (b) 4o before and after UV (λ_irr. = 254 nm) irradiation in n-hexane (λ_ex = 292 nm for 2o, and 301 nm for 4o).

The thermal cycloreversion kinetics of compound 2c were systematically investigated in toluene solution across multiple temperatures. As shown in Fig. S29, the time-dependent absorbance decay profiles of the closed isomer 2c followed first-order kinetics. Through Arrhenius analysis of the temperature-dependent rate constant, the activation energy (E_a) for the thermal back reaction was determined to be 73 kJ mol⁻¹. Moreover, three key factors may contribute to the accelerated thermal relaxation of 2c: (i) low activation energy (E_a) comparing to that typical diarylethenes; (ii) thermodynamic stabilization of the open isomer relative to the closed isomer (Fig. 1); (iii) aromaticity restoration in naphthalene side chains during cycloreversion. These combined effects result in a remarkably short half-life (t_1/2 = 60.8 min at 293 K) for the closed isomer. This rapid self-erasing capability positions 2c as an ideal candidate for dynamic photochromic applications requiring fast resetting, such as adaptive eyewear and real-time optical sensors.

3. Conclusions

This study integrates naphthalene side chains into diarylethene derivatives to achieve light-controlled modulation of photochromic reactivity and aromaticity, advancing the design of optical materials. Cyclization of the diarylethene core under light selectively alters conjugation pathways, impacting specific naphthalene rings’ aromaticity, as evidenced by NICS calculations and bond character analysis, which link structural changes to shifts in electron delocalization and photochromic behavior. The closed isomer 4c exhibits fluorescence quenching due to enhanced non-radiative decay, enabling real-time monitoring of photostationary states, while rapid thermal reversion ensures reversibility. To validate the structure–function relationship, the photochemical behavior of derivatives 1o–4o was systematically investigated across different solvents, probing environmental and structural influences on photochromism and aromaticity. These derivatives offer promise for next-generation photonic devices, such as optical switches and sensors, illustrating how molecular engineering can synergize photochromism and electronic tuning to tailor advanced functionalities.

Author contributions

Tao Ou: validation, investigation, writing – original draft; Lingxu Kong: validation, investigation, writing – original draft; Changsen Song: investigation; Bingyan Shang: investigation; Jingjing Yang: investigation; Jinxin Zuo: investigation; Feifan Di: investigation; Maocai Yan: validation; Lin Ding: methodology, validation, writing – review & editing; Ruiji Li: conceptualization, methodology, validation, investigation, writing – original draft, writing – review & editing, supervision.

Conflicts of interest

There are no conflicts to declare.

Data availability

All experimental and computational data supporting this study are available within the manuscript and its SI. Supplementary information: (1) Synthetic procedures & compounds characterization: full experimental details for dinaphthylethene derivatives 1o–4o, NMR spectra (¹H, ¹³C), HR-MS data, X-ray crystal analysis data. (2) Photochemical datasets: UV-Vis absorption spectra (open/closed isomers), fluorescence emission spectra and quenching kinetics, thermal back-reaction rate constants (k) and activation energy (E_a) calculations. (3) Computational data: NICS(1)zz calculation results, bond length/order analyses for naphthalene rings, Cartesian coordinates of optimized structures (open/closed isomers). (4) Raw kinetics traces: time-resolved spectroscopy data for photostationary state monitoring. See DOI: https://doi.org/10.1039/d5nj03137k.

CCDC 2478062–2478065 contain the supplementary crystallographic data for this paper.^37a–d

Acknowledgements

This research was funded by Shandong Provincial Natural Science Foundation, grant number ZR2021QB124, Outstanding Youth Foundation (Overseas) Project of Rizhao City Natural Science Foundation, grant number RZ2021ZR1.

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Footnote

† These authors contributed equally to this work.

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