Linear and non-linear optical response properties of β-enamino ketones

First Hyperpolarizabilities of Intramolecular Charge-Transfer Architectures Based on Acenaphthene Derivatives in Gas, Solution, and Solid States

Constructing charge transfer (CT) systems and packing arrangement are common and effective methods to control the efficiency of nonlinear optical (NLO) materials. Apart from the traditional through-bond CT (TBCT) systems, through-space CT (TSCT) also leads to distinctive optical and electronic properties. Meanwhile, corresponding theoretical investigations of the aggregation effect are highly desired. In this work, some TSCT and model compounds incorporating acenaphthene as a scaffold and triphenylamine (TPA) as the donor are theoretically performed to systematically reveal the effect of both solvent and solid environments on their static first hyperpolarizabilities (β_tot) by using the polarizable continuum model (PCM) and the combined quantum mechanics and molecular mechanics (QM/MM) method. Results indicate that the dichloromethane solvent effect within the PCM approach causes an almost 2 times increase of the β_tot values. Besides, the different packing modes and intermolecular interactions have remarkable influence on the second-order NLO properties. For the case of TPA-ace-CN in the crystal state, the parallel arrangement will lead to large NLO responses (4.9 × 10^-30 esu) compared to the correspondingly isolated molecule (3.4 × 10^-30 esu). However, for the TPA-ace-TRZ compound with the TSCT architecture, selection of the molecular arrangement may make the aggregate ineffective due to the offset of the through-space dipole and charge transfer between D-A groups, which lead to the β_tot values decreasing from 15.2 × 10^-30 to 7.7 × 10^-30 esu. We believe that our calculation will serve as a guide for the exploration of more efficient NLO materials wherein the molecules are oriented in their most favorable arrangements.

Syntheses and structures of two benzoyl amides: 2-chloro-4-eth-oxy-3,5-dimeth-oxy-N-(3-oxo-cyclo-hex-1-en-1-yl)benzamide and 2-chloro-N-(5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl)-4-eth-oxy-3,5-di-meth-oxy-benzamide

The first title benzoyl amide, C₁₇H₂₀ClNO₅ (3a), crystallizes in the monoclinic space group P2₁/c with Z = 4 and the second, C₁₉H₂₄ClNO₅ (3b), also crystallizes in P2₁/c with Z = 8 (Z' = 2), thus there are two independent mol-ecules in the asymmetric unit. In 3a, the phenyl ring makes a dihedral angle of 50.8 (3)° with the amide moiety with the C=O group on the same side of the mol-ecule as the C-Cl group. One meth-oxy group is almost in the plane of the benzene ring, while the eth-oxy and other meth-oxy substituent are arranged on opposite sides of the ring with the eth-oxy group occupying the same side of the ring as the C=O group in the amide moiety. For one of the two mol-ecules in 3b, both the amide and 5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl moieties are disordered over two sets of sites with occupancies of 0.551 (2)/0.449 (2) with the major difference between the two conformers being due to the conformation adopted by the cyclo-hex-2-en-1-one ring. The three mol-ecules in 3b (i.e., the undisordered mol-ecule and the two disorder components) differ in the arrangement of the subsituents on the phenyl ring and the conformation adopted by their 5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl moieties. In the crystal of 3a, N-H⋯O hydrogen bonds link the mol-ecules into a zigzag chain propagating in the [001] direction. For 3b a combination of C-H⋯O and N-H⋯O inter-molecular inter-actions link the mol-ecules into a zigzag ribbon propagating in the [001] direction.

Tuning of hyperpolarizability, and one- and two-photon absorption of donor-acceptor and donor-acceptor-acceptor-type intramolecular charge transfer-based sensors

The present work aims to study the effect of solvent as well as arrangement of donor-acceptor groups on linear and non-linear optical (NLO) response properties of two experimentally studied intramolecular charge-transfer (ICT)-based fluorescent sensors. One of them (molecule 1) is a donor-acceptor (D-A) system with hemicyanine and dimethylanilino as electron withdrawing and donating groups, respectively, while the other one (molecule 3) is molecule 1 fused with a boron-dipyrromethene (BODIPY) moiety. BODIPY acts as the electron acceptor group of molecule 2 that as well consists of dimethylanilino as the electron donor. Density functional theory (DFT) as well as time-dependent DFT has been employed to optimize the geometry of the molecules, followed by computation of dipole moment (μ), static first hyperpolarizability (β_total), and one- and two-photon absorption (TPA) strengths. The results reveal that dipole moment as well as total static first hyperpolarizability (β_total) of the studied molecules is dominated by the respective components in the direction of charge transfer. The ratio of vector component of first hyperpolarizability (β_vec) to β_total also supports the unidirectional charge transfer in the studied systems. In molecule 3, which is a donor-acceptor-acceptor (D-A-A)-type system, the BODIPY moiety is found to play a major role in controlling the NLO response over the other acceptor group. Solvents are also found to play an important role in controlling the linear as well as NLO response of the studied systems. A significant increase in the first hyperpolarizability as well as TPA cross-section of the studied molecules is predicted due to an increase in the dielectric constant of the medium. The results presented are expected to provide a clue in tuning the NLO response of many ICT-based chromophores, especially those with D-A-A arrangements.