A new class of redox metallopolymer based on cyclometalated iridium(III) centers is described, with unusually intense luminescence properties in aqueous media. We report the facile synthesis, photophysical and electrochemical characterization, supported by DFT calculations and their electrochemiluminescence (ECL) properties which, under some circumstances, are significantly greater than the analogous ruthenium-based materials. The photoluminescence (PL) and ECL of these materials are further dramatically enhanced when dispersed or immobilized as polymeric nanoparticles (PNPs). This aggregation-induced emission (AIE and AIECL) operates by providing important protection for the cyclometalated iridium(III) centers against the types of quenching processes which commonly afflict iridium-based luminophores in aqueous media. The results suggest interesting new avenues of research for the application of such materials in and PL and ECL-based detection and imaging as well as light-emitting devices.
We
present the first benchmarking study of nonadiabatic
matrix
coupling elements (NACMEs) calculated using different density functionals.
Using the S
1 → S
0 transition in perylene solvated in toluene as a case
study, we calculate the photophysical properties and corresponding
rate constants for a variety of density functionals from each rung
of Jacob’s ladder. The singlet photoluminescence quantum yield
(sPLQY) is taken as a measure of accuracy, measured experimentally
here as 0.955. Important quantum chemical parameters such as geometries,
absorption, emission, and adiabatic energies, NACMEs, Hessians, and
transition dipole moments were calculated for each density functional
basis set combination (data set) using density functional theory based
multireference configuration interaction (DFT/MRCI) and compared to
experiment where possible. We were able to derive simple relations
between the TDDFT and DFT/MRCI photophysical properties; with semiempirical
damping factors of ∼0.843 ± 0.017 and ∼0.954 ±
0.064 for TDDFT transition dipole moments and energies to DFT/MRCI
level approximations, respectively. NACMEs were dominated by out-of-plane
derivative components belonging to the center-most ring atoms with
weaker contributions from perturbations along the transverse and longitudinal
axes. Calculated theoretical spectra compared well to both experiment
and literature, with fluorescence lifetimes between 7.1 and 12.5 ns,
agreeing within a factor of 2 with experiment. Internal conversion
(IC) rates were then calculated and were found to vary wildly between
106–1016 s–1 compared
with an experimental rate of the order 107 s–1. Following further testing by mixing data sets, we found a strong
dependence on the method used to obtain the Hessian. The 5 characterized
data sets ranked in order of most promising are PBE0/def2-TZVP, ωB97XD/def2-TZVP,
HCTH407/TZVP, PBE/TZVP, and PBE/def2-TZVP.
A post-synthetic modification and metallation procedure has been used to prepare a family of heterobimetallic Au(I)-Ag(I) and Au(I)-Hg(II) complexes featuring either symmetrical or asymmetrical bis-N-heterocyclic carbene ligands with methylene or...
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