Theoretical studies on the nonlinear optical properties of zwitterionic organic molecules: effect of π–σ–π through-bond coupling on the first hyperpolarizability1IICT Communication No. 4123.1

First hyperpolarizability of some nonconjugated donor–acceptor 3D molecules: noncentrosymmetric crystal through conformational flexibility

“…Since these molecules involve charge transfer over nonconjugated bonds this study also provides some understanding of the mechanistic aspects of this phenomenon, a topic which has been explored little so far. 20,[54][55][56][57]…”

DFT study of NLO properties of boroxine based octupolar molecules

“…In early 1990s, Zyss introduced the concept of octupolar molecule, with 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) 8,12,14 as typical example, which is characterized by a non dipolar and non-centrosymmetric planar C 3h or D 3h molecular symmetry. Since then, increasing research attention has been focused on NLO active octupolar molecules, including the extension from planar two dimensional systems, like trisubstituted benzenes (triphenylbenzenes) 15 , hexasubstituted benzenes ( tricyanobenzenes , trinitrobenzenes, trimethoxybenzenes and phenylacetylene mesitylenes) [16][17] , 1,3,5-triazines [18][19][20][21][22] , to D 2 , D 3 , or T d characterized three-dimensional ones [23][24] . An advantage of octupolar molecules is that they seem likely to crystallize in noncentrosymmetric space groups due to the lack of ground state dipole moment.…”

Enhanced Nonlinear Optical Response in Zwitterionic Molecules: A Computational Study on the Role of Orbital Interactions through σ Bonds

“…We have also observed, by theoretical calculations, with aromatic D and A that if NLO activity has to be enhanced in a D-σ-A system, then the conformation of the molecule should be in such a way that the TBI is maximized. [20][21] In this work, we show that by attaching an electron withdrawing functional group at the acceptor end of a σ-bonded heterocyclic zwitterion, there is a larger charge separation and more intense CT. This leads to 0 values enhanced at least by 10-15 times than that of the molecules without the electron withdrawing functional groups.…”

“…This Work. Most of the studies on hyperpolarizabilities reported in the literature have been on π-electron conjugated systems, and there are only a few reports on σ-bonded donor−acceptor systems. − In the case of charge separated systems, to the best of our knowledge, experimental studies on the static β of zwitterionic σ-bonded molecules have not been carried out. One zwitterionic crystal structure (structure 1 ) in which the D and A are linked by a σ-bond has been reported for NLO applications, but the β value for this system has not been estimated either theoretically or experimentally .…”

“…One zwitterionic crystal structure (structure 1 ) in which the D and A are linked by a σ-bond has been reported for NLO applications, but the β value for this system has not been estimated either theoretically or experimentally . In an earlier work on computational design of zwitterionic molecules to achieve charge separation, we inserted a σ-spacer between the aromatic donor and acceptor ring . The σ-bond breaks the conjugation and enforces zwitterionic behavior while the π−σ−π through bond interaction (TBI) leads to a low energy CT.…”