Intramolecular rate-constant calculations based on the correlation function using temperature dependent quantum Green's functions.
Phys Chem Chem Phys
; 26(5): 4151-4158, 2024 Jan 31.
Article
in En
| MEDLINE
| ID: mdl-38230411
ABSTRACT
A theoretical method for calculating rate constants for internal conversion (IC), intersystem crossing (ISC) and radiative (R) electronic transitions is presented. The employed method uses temperature-dependent quantum Green's functions, which give the opportunity to consider almost any nth-order polynomial perturbation operator and the influence of external electromagnetic fields on the rate constants. The rate constants of the IC, ISC and R processes are calculated for two important indocyanine molecules namely indocyanine green (ICG) and heptamethine cyanine (IR808) at the Franck-Condon level using the temperature-dependent quantum Green's function approach. Calculations at the time-dependent density functional theory level with the MN15 functional show that ICG and IR808 have only one triplet state below the S1 state. The main deactivation channel of the S1 state is the IC process with a large (kIC(S1 â S0)) rate constant of â¼109-1011 s-1. The estimated quantum yield of fluorescence (φfl) is â¼0.001-0.24 for the two studied molecules, which agrees rather well with experimental values. Thus, the present approach enables calculations of the three kinds of rate constants and the quantum yield of fluorescence using the same computational methodology.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Phys Chem Chem Phys
Journal subject:
BIOFISICA
/
QUIMICA
Year:
2024
Document type:
Article
Affiliation country:
Finland
Country of publication:
United kingdom