Dipolar Donor-Acceptor-Substituted Schiff Base Complexes with Large Off-Diagonal Second-Order Nonlinear Optical Tensor Components

Abstract

The synthesis, characterization, and two-dimensional second-order nonlinear optical (NLO) response of a dipolar NiII donor- acceptor Schiff base complex and the related ligand are reported. Electric-field-induced second-harmonic generation and harmonic light (hyper-Rayleigh) scattering techniques, in combination with INDO/SCI-SOS theoretical calculations, were used to investigate the vector part of the hyperpolarizability tensor and the two-dimensional character of the molecular nonlinearity, respectively. Off-diagonal hyperpolarizability tensors can be related to charge-transfer transitions that are polarized perpendicular to the molecular dipolar axis, while parallel transitions account for the diagonal hyperpolarizability tensor. The role of the metal center in enhancing the two-dimensional NLO response of such molecules is twofold since it acts both as the donor and the bridging moiety of the planar donor-(pi-conjugate-bridge)-acceptor system. These dipolar two-dimensional molecules are interesting candidates from the perspective of polarization-independent NLO materials.

First hyperpolarizabilities of vinylogue organometallic sesquifulvalene chromophores: A DFT study

“…The previous theoretical investigations on molecular organometallic NLO properties have mostly employed the semi‐empirical quantum chemical methods 12–15, which have been remarkably successful in the understanding of optical nonlinearities of organometallics. For example, Kanis et al 16 carried out a systemic study of the LO and NLO properties for some neutral organometallic ferrocenyl chromophores at ZINDO/sum‐over‐state (SOS) level.…”

Theoretical study on the nonlinear optical properties of donor/acceptor-functionalized trigonal dehydrobenzoannulenes

“…1), we have designed 6 derivatives (see [2][3][4][5][6][7] in Fig. 1) in order to study how the p-conjugated bond and positions of donor (D) or acceptor (A) affect the NLO properties of DBA derivatives.…”

“…Recently, it has been suggested that two-dimensional charge transfer (2DCT) chromophores can circumvent these problems [7,8]. 2DCT chromophores which possess multiple donor-acceptor substituents, such as ''K-shaped" [9], ''X-shaped" [10], ''Y-shaped" [11], ''U-shaped" [12], ''H-shaped" [13], have a 2D b tensor character, where the off-diagonal components become significant.…”

A theoretical study on the efficient reversible redox-based switching of the second-order polarizabilities of two-dimensional nonlinear optical-active donor–acceptor phenanthroline-hexamolybdate

“…In contrast, the anisotropy values were reduced to 0.51 and 0.32 in compounds Ib and IIb, respectively, due to a departure from the planarity of the pyramid amido with the electron-donating 4-ethynylbenzenamine substitution. Compounds Ib and IIb likely do not exhibit relatively significant 2D NLO properties when compared to the corresponding unsubstituted compounds Ia and IIa, while they still display typical values of 2D donor-acceptor bis(salicylaldiminato)Ni II Schiff base complexes (NiL) and the related ligands (H 2 L) [36].…”