Influence of orthogonal di- and trimerization leading to meso fused BODIPY on linear and NLO properties - TDDFT study and singlet-triplet energy distribution

[Display omitted] •meso fused BODIPY dyes were studied for NLO properties.•Pure, global hybrid and range separated hybrid functional were employed.•Dimerization affect the value of Linear Polarizability and dipole moment.•Singlet-triplet energetic gap were evaluated theoretically. Orthogonally dimeric meso attached dipyrromethene dyes are examined using computational tools with help of pure, RSH and GH functionals using 6-311++G(d,p) basis set for their steady-state absorption, nonlinear optical characteristics, and singlet-triplet distribution. The vertical excitations of the corresponding oscillator strengths are determined using B3LYP, BHHLYP and CAM―B3LYP using 6-311++G(d,p) method while nonlinear optical properties were established with help of pure, RSH and GH functionals. Dimerization affects the linear polarizability. The insertion of formyl group at 2 and 6 position of BODIPY dyes increases the value of first and second-order hyperpolarizability. The functional CAM―B3LYP is found to be closer in predicting the λabs. The “HOMO-LUMO” energy gap of EA2 was found to be the least which might be attributed to the presence of electron accepting formyl group. The introduction of formyl group and dimerization result in enhancement of dipole moment of these BODIPY dyes. Benchmarking study of proper functionals (pure, GHs and RSHs) to estimate the polarizability values reveal that the lowest value of MSE was found in the case of pure functional for the tHCTH and VSXC (MSE = 0.02 × 10−24 esu). The lowest value of MSE was found in case of GH functional for the M062X (MSE = 0.14 × 10−30 esu) evidence the benchmarking to calculate the first-order polarizability for these dyes. For second-order polarizability (γ0), the lowest value of MSE was found in case of GH for the BMK (MSE = 2.37 × 10−36 esu) evidence the benchmarking for these dyes. The calculated energy difference between E(S1) and E(T1) is following the essential criteria for the singlet fission i.e. E(S1) > 2E(T1) and the difference value found to be positive. The singlet triplet energetic difference (ΔEST) was found to be more precise with CAM―B3LYP and BHHLYP functional compared to B3LYP functional.