Abstract
The present study explores a series of novel donor-as-acceptor (D-as-A) molecules containing 4,4'-dimethyldiphenylamine moiety as donor, 4,4'-dinitrodiphenylborane as acceptor while different as bridges as efficient linkers between them, which comprises of ( - HC = CH - )(n), ( - Ph - )(n) and ( - Ph HC = CH - )(n) combinations for compounds in series 1, 2 and 3, respectively. Quantum chemical computations are applied to calculate the linear polarizability (alpha), first (beta) and second (gamma) hyperpolarizabilities. A comparative analysis is performed considering an increase of NLO polarizabilities as a function of different as-linkers. Among the investigated compounds, 3c shows the largest first and second hyperpolarizabilities of 1378 x 10(-30) and 34971 x 10(-36) esu, respectively. Interestingly, an increase in NLO polarizability is observed by modifying the pi-conjugated bridges and the largest NLO polarizability is observed for series 3 possessing (Ph HC = CH - )(n) as-linker which is found due to its lower transition energy and higher oscillator strengths. Furthermore, TD-DFT investigations, frontier molecular orbitals (FMOs) and electron density difference (EDD) maps analysis have shown a more efficient intramolecular charge transfer character from donor to acceptor moieties through (Ph HC = CH-)(n) as-linkers. The density of states (DOS) maps are showing explicit contributions of electronic states from different fragments of a molecular system where the partial contributions of (Ph HC = CH-)(n) pi-linkers is seen significant in HOMO-LUMO orbitals of all the systems in series number 3. Thus, we believe that our study will highlight the importance of different D-pi-A chromophores having variant types of pi-conjugation cores as discussed in the present investigation. (C) 2020 Elsevier Inc. All rights reserved.