Organic linkers control the thermosensitivity of the emission intensities from Tb(iii) and Eu(iii) in a chameleon polymer

Thermosensitivity of emission intensity in a polymer comprised Tb3+ and Eu3+ can be controlled by the energy level of the organic linker-centered triplet state as well as that of the ligand-centered triplet state.


Rate constants for emission and quenching
According to the transition state theory, the rate constant k can be written where kB is Boltzmann's constant, h is Plank's constant, T is temperature, R is the gas constant, G ‡ is the free energy of activation, and  is the transmission coefficient which is often taken as 1. The spin-orbit effect needs to be considered because the spin multiplicity changes at the T1/S0 crossing point ((6) in Fig. 2). The rate constant (1), however, can be approximately treated like a spin-allowed transition because Ln 3+ has a large spin-orbit coupling constant. Table S1 shows the quenching rate constants estimated for  = 1 and G ‡ = 13.1 and 22.5 kcal mol -1 for Tb 3+ and Eu 3+ complexes, respectively. 200 2 × 10 -2 1 × 10 -12 300 2 × 10 3 3 × 10 -4 400 6 × 10 5 4 × 10 0 500 2 × 10 7 5 × 10 3 The rate constant for Tb 3+ emission is 1×10 3 s -1 , which is estimated from the experimental lifetime of Tb(hfa)3(tppo)2 at 80 K (0.8 ms). That for Eu 3+ is 1 × 10 3 s -1 , which is estimated from the experimental lifetime of [Eu(hfa)3(dpbp)] at 300 K (0.85 ms). (Note that the barrier for quenching in Eu 3+ with hfa is large enough, thus the lifetime at 300 K is applicable to estimate k.) As shown above, the quenching rate constants at 300 K for Tb 3+ and 500 K for Eu 3+ are comparable to the emission rate constants. S3

Model complex for the chameleon [Ln(hfa)3(dpbp)]n (Ln = Eu and Tb)
The shapes of the PESs of the ground state and Ln 3+ -centered excited states for a system including two Ln 3+ are nearly identical when the distance between Ln 3+ are enough long to ignore their interaction. Thus, in the case of the chameleon polymer, in which the distance between Tb 3+ and Eu 3+ is 13.6 Å, the PESs of Tb 3+ -and Eu 3+ -centered excited states can be described by that of the ground state corrected by the energy shift parameters, 580 and 490 nm, respectively. Figure S2 shows the schematic image of the PESs of the ground and excited states related to the EET from Tb 3+ to Eu 3+ . Figure S2. Schematic illustration of the PESs for the ground and excited states in the chameleon polymer. The ground state and Tb 3+ -, Eu 3+ -, dpbp-centered excited states are in blue, green, pink, and red, respectively. The notation (S0, 7 F6, 7 F0) represents the electronic states of the dpbp, Tb, and Eu, are S0, 7 F6, and 7 F0, respectively.
The chemical structure of the chameleon model complex is shown in Figure S3. The initial structure was obtained by the crystal structure (CCDC: 855863). The electronic energies were evaluated by two ONIOM schemes. The high-level regions of the ONIOM schemes (I) and (II) are shown in green and red, respectively. The density functional theory (DFT) method with the same basis set in the section 1.1 and the MM method with the UFF force parameters [S2] and the QEq charges [S3] were used for the high-and low-level calculations. The atoms in low-level region were fixed during the geometry optimization. Figure     Blue, red, green, pink, and yellow are the local minima on the ground state, dpbp-centered T1, and the minimum energy crossing points for the EET between T1 and 5 D4 of Tb, the EET between T1 and 5 D0 of Eu, and ISC processes, respectively.

Model complexes with different linker molecules (dpb, dppcz, dpbt)
The chemical structures of the model complexes with the linker molecules (dpb, dpppcz, and dpbt) are shown in Figure S6. The initial structures were obtained by the crystal structures (CCDC: 855862,855865,and 855864). [34] The electronic energies were evaluated by the ONIOM(B97XD:UFF) scheme where the linker molecule and others are treated as high-and low-level regions, respectively.
The geometrical optimizations of the critical points (shown in Figure S7) were carried out with fixing the atoms in the low-level regions.   Figure S6. Blue, red, green, pink, and yellow are the local minima on the ground state, the linker-centered T1, and the minimum energy crossing points for the EET between T1 and 5 D4 of Tb, the EET between T1 and 5 D0 of Eu, and ISC processes, respectively.

Figure S8
. Potential energy profiles (in kcal mol -1 ) of the isolated linker molecules calculated by the B97XD/cc-pVDZ level of theory. Blue and red are S0 and T1 states, respectively.   Table S4. Energy levels (kcal mol -1 ) of the N-th triplet states of the model complexes in Figure S9 calculated with TDDFT method. 1 (The energy zero is 5 D4. See Figure 5)  3+ and Eu 3+ and cc-pVDZ were used for others. The structures are based on the optimized structure of the ground state with ONIOM(B97XD:UFF) shown in Figures 5 and 6. Figure S10(a). Natural transition orbitals of the N-th (N = 1-7) triplet states calculated using the full-QM TDDFT method for the model complex comprising dpbp shown in Figure S9

Optical measurements.
Temperature-dependent emission spectra from 100 K to 450 K in solid state for the Chameleon polymers ( Figure 7) were recorded on a HORIBA Fluorolog-3 spectrofluorometer with a cryostat (Thermal Block Company, SA-SB245T) and a temperature controller (Oxford, Instruments, ITC 502S), and corrected for the response of the detector system. S10