From luminescence quenching to high-efficiency phosphorescence: a theoretical study on the monomeric and dimeric forms of platinum(ii) complexes with both 2-pyridylimidazol-2-ylidene and bipyrazolate chelates

Abstract

To develop the solid-state light-emitting materials with high luminescence efficiency, the potential photophysics and luminescence mechanism of aggregation state remains a challenge and a priority. Here, we apply density functional...

Reducing the internal reorganization energy via symmetry controlled π-electron delocalization

“…15–17 The inner-sphere reorganization energy mainly includes contributions from geometry relaxations in the excited state caused by charge injection or electronic transition processes. 18–23 In practice, the inner-sphere reorganization energy may be suppressed by increasing the molecular rigidity in the solid matrix incorporating stacking and/or self-assembly, 24–28 or by decreasing the bond length variation upon excitation via extending the π conjugation skeleton or enhancing the local non-bonding characteristics in organic molecules. 29–32 Alternatively, a lower reorganization energy has also been observed in systems with higher molecular symmetry and/or more delocalized molecular orbitals.…”

Efficient red thermally activated delayed fluorescence emitters achieved through precise control of excited state energy levels

“…38,39 In order to reliably describe the characteristics and energies of excited states, it is crucial to correctly select quantum chemical (QC) methods such as density functional theory (DFT) 40 or wavefunction-based electron correlation methods. 41,42 For time-dependent DFT (TD-DFT) 43 calculations, non-hybrid functionals neglect the long-range Coulomb interaction between the separated hole and electron, which greatly underestimates the transition energy of CT states. 44 For the pure Hartree–Fock (HF) functional, due to the high proportion of exchange terms, it encounters serious electronic correction problems and significantly overestimates the excitation energy of the system.…”

“…2 , with concurrent listing of the root mean square displacements (RMSD). 42 In addition, based on the optimized S 0 /S 1 geometries, the absorption and emission data of the emitters in toluene solution obtained by the TD-DFT/PBE0-1/3 method are also provided in Table 1 . As depicted in Fig.…”

Design of Near-Infrared-Triggered Metallo-Photosensitizers via a Self-Assembly-Induced Vibronic Decoupling Strategy

“…The phosphorescence radiative transition is another decay process, which is supposed to be efficient for IrHA1 due to the large SOC constant of the iridium atom. According to the equation of triplet radiative rate constant ( k r , eq S1), k r depends on both SOC and the S n → S 0 transition dipole moment ( M s n ). Our calculation results (Figure S16) show that the M s n ( n = 1–10) values are small due to the small overlap of the hole and electron in the S n → S 0 transition, which is beneficial for reducing k r , thereby maximizing the 1 O 2 generation of IrHA1.…”