D-π-A'-π-A chromophores with quinoxaline core in the π-electron bridge and charged heterocyclic acceptor moiety: Synthesis, DFT calculations, photophysical and electro-chemical properties

A novel stilbazolium derivative crystals of 4-[2-(4-dimethyl amino-phenyl)-vinyl]-1-methyl-pyridinium+ bromide- (DMSB) single crystal: exploration of the growth, molecular structure, linear optical, and third order nonlinear properties

A novel third-order stilbazolium derivative single crystal, 4-[2-(4-dimethyl amino-phenyl)-vinyl]-1-methyl-pyridinium bromide (DMSB), was fruitfully harvested using methanol as a medium, through a slow evaporation technique. The solubility of the prepared DMSB powder was experimentally tested at different temperatures (30 °C to 50 °C) with a methanol solvent. Single crystal X-ray diffraction analysis (SCXRD) implied that the DMSB crystal crystallized in a centrosymmetric fashion (space group P21/c) with the monoclinic crystal system. The molecular weight of the element present in DMSB was confirmed by CHN elemental analysis. Nuclear magnetic resonance (NMR) spectroscopic study confirmed the molecular structure of the DMSB crystal. All the functional group vibrations raised from the title compound were studied using Fourier transform infrared spectroscopy (FTIR). From the UV-visible spectrum, the absorbance nature and band gap of the grown DMSB crystal were determined. The photoluminescence study of the grown crystal exhibited an emission peak at 660 nm, which is attributed to the red light emission in the EM spectrum. The morphological characteristics of the crystal were characterized using atomic force microscopy (AFM). Hirshfeld surface analysis was employed to quantitatively explore the non-covalent interactions that are accountable for the crystal packing. The third-order nonlinear susceptibility was determined experimentally and it was found to be 1.6 × 10-8 esu. These favourable Z-scan analysis results indicate that the DMSB crystal is a good candidate for different applications, such as photonics devices, optical computing, optical switches, and optical limiting.

Synthesis of D-π-A'-π-A Chromophores with Quinoxaline Core as Auxiliary Acceptor and Effect of Various Silicon-Substituted Donor Moieties on Thermal and Nonlinear Optical Properties at Molecular and Material Level

Novel D-π-A'-π-A chromophores with quinoxaline cores as auxiliary acceptors and various donor moieties (aniline, carbazole, phenothiazine, tetrahydroquinoline) containing bulky tert-butyldimethylsilyloxy (TBDMSO) groups and tricyanofuranyl (TCF) acceptors with bulky cyclohexylphenyl substituents were synthesized via eight- to nine-step procedures, and their photo-physical and thermal properties were investigated. The values of the chromophores' first hyperpolarizabilities were calculated in the framework of DFT at the M06-2X/aug-cc-pVDZ computational level; the effect of the introduction of the TBDMSO group into the donor fragment is shown to be inessential, as this group is not coupled to the π-conjugated system of the chromophore. The chromophore with the tetrahydroquinoline donor has a first hyperpolarizability value of 937 × 10^-30 esu, which is the highest for the studied chromophores. Atomistic modeling of composite materials with the studied chromophores as guests demonstrated that the presence of bulky substituent in the donor fragment prevents notable aggregation of chromophores, even at high chromophore content (40 wt.%). The nonlinear optical performance of guest-host materials with 25 and 40 wt.% of suggested chromophore content was studied using a second harmonic generation technique to give the NLO coefficient, d₃₃ up to 52 pm/V.

Composing NLO Chromophore as a Puzzle: Electrochemistry-based Approach to Design and Effectiveness

A series of D-π-A, D-π-D'-π-A, D-π-A'-π-A nonlinear optical chromophores with vinylene π-electron bridges or bridges with π-deficient/π-excessive heterocyclic moieties along with the corresponding precursors D-vinylene, D-π-D', D'-π-A, D-π-A' and A'-π-A are synthesized and studied both experimentally and computationally. The effect of the heterocycle in the π-electron bridge on the oxidation/reduction potentials and the energy gap (ΔE^el ) is investigated in detail. The properties of the D-π-A'(D')-π-A chromophores are shown to correlate with those of building blocks: the oxidation potential is determined by the D-vinylene, and the reduction potential is determined by A'(D')-π-A truncated compounds. The contribution of the acceptor to the oxidation potential of chromophores in comparison with those of the precursors was estimated and analyzed in terms of electronic communication between the end groups. A good correlation between the ΔE^el and the chromophores' first hyperpolarizability is revealed.