New organic non-linear optical materials of stilbene and diphenylacetylene derivatives

Enriching NLO efficacy via designing non-fullerene molecules with the modification of acceptor moieties into ICIF2F: an emerging theoretical approach

Non-fullerene (NF)-based compounds have attracted much attention as compared to fullerene-based materials because of their promising optoelectronic properties, lower synthetic cost and greater stability. Usually, the end-capped groups have a promising impact in magnifying the nonlinear optical (NLO) characteristics in the non-fullerene molecules. Based on this, a series of new NLO active non-fullerene molecules (NFAD2-NFAD6) have been established. The non-fullerene molecules (NFAD2-NFAD6) were designed by end-capped modification in acceptor moieties of the reference (NFAR1), while donor and π-bridge moieties were kept the same in the entire series. Quantum chemistry-based calculations at the M06/6-311G(d,p) level were done to determine the NLO characteristics and for other supportive analyses. The acceptor and donor moieties were utilized at the opposite terminals of NFAD2-NFAD6, which proved to be an effective approach in tuning the FMO band gap. Overall the results of natural bond orbital (NBO), density of state (DOS) and transition density matrices (TDMs) analyses supported the NLO properties of the designed compounds. Among all the studied compounds, NFAD4 was proven to be the most suitable candidate due to its promising NLO properties, well supported by a lower bandgap of 1.519 eV and a maximum absorption wavelength of 999.550 nm. Therefore, NFAD4 was reported with greater amplitude of dipole polarizability (10.429 e.s.u), average polarizability (2.953 × 10^-22 e.s.u), first hyperpolarizability (13.16 × 10^-27 e.s.u.) and second hyperpolarizability (2.150 × 10^-31 e.s.u.) than other derivatives and NFAR1. Subsequently, the present study depicted the significance of utilizing different non-fullerene (NF)-based acceptor moieties to achieve the promising NLO material. This computational study may lead towards new plausible pathways for researchers to design potent NLO substances for impending hi-tech applications.

Nonlinear optical properties of diaromatic stilbene, butadiene and thiophene derivatives

Stilbene and butadiene derivatives display NLO activity with SHG intensities up to 32 times to that of urea for 2-chloro-3,4-dimethoxy-4′-nitrostilbene.

Syntheses of NLO diamino chromophores containing imidazole and thiophene rings as conjugation linkage

Three nonlinear optical chromophores bearing diamino groups have been synthesised, in which imidazole and thiophene rings were employed as elongated conjugation bridges.

Selective preparation of elusive and alternative single component polymorphic solid forms through multi-component crystallisation routes

A transferable, simple, method for producing previously elusive and novel polymorphic forms of important active pharmaceutical ingredients (APIs; paracetamol (acetaminophen), piroxicam and piracetam) is demonstrated. Nitrogen heterocyclic co-molecules are employed to influence the self-assembly crystallisation process in a multi-component environment. Previously unknown solvates have also been synthesised by this method.

Comment on the paper "Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): a potential NLO material" by P.M. Dinakaran, S. Kalainathan [Spectrochim. Acta A 111 (2013) 123-130]

We argue that (trans)-4-chloro-4'-nitrostilbene is not a new organic nonlinear optical material as claimed by Dinakaran and Kalainathan [P.M. Dinakaran, S. Kalainathan, Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-Chloro 4-Nitrostilbene (CONS): a potential NLO material, Spectrochim. Acta A 111 (2013) 123-130], but instead a well-known compound whose synthesis, spectral data, single crystal structure and second harmonic generation (SHG) efficiency are well documented in the literature. The title paper is completely erroneous.

Synthesis, growth, structural, optical, spectral, thermal and mechanical studies of 4-methoxy 4-nitrostilbene (MONS): a new organic nonlinear optical single crystal

4-Methoxy 4-nitrostilbene (MONS), a new organic nonlinear optical material has been synthesized. Based on the solubility data good quality single crystal with dimensions up to 38×11×3 mm(3) has been grown by slow evaporation method using ethyl methyl ketone (MEK) as a solvent. Powder XRD confirms the crystalline property and also the diffraction planes have been indexed. The lattice parameters for the grown MONS crystals were determined by using single crystal X-ray diffraction analysis and it reveals that the crystal lattice system is triclinic. The crystalline perfection of the grown crystals has been analysed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectrum for powdered MONS sample confirms the functional groups present in the grown crystal. The UV-vis absorption spectrum has been recorded in the range of 190-1100 nm and the cut off wavelength 499 nm has been determined. The optical constants of MONS have been determined through UV-vis-NIR spectroscopy. The MONS crystals were further subjected to other characterizations. i.e., (1)H NMR, TG/DTA, photoluminescence and microhardness test. The Kurtz and Perry powder technique confirms the NLO property of the grown crystal and the SHG efficiency of MONS was found to be 1.55× greater than that of KDP crystal.

Linear optical transmission measurements and computational study of linear polarizabilities, first hyperpolarizabilities of a dinuclear iron(III) complex

The optical transmission spectral study of a dinuclear metal complex [FeL(MeOH)Cl]2 (L=N-(5-methylphenyl)-3-methoxysalicylaldimine) has been carried out. The linear optical characterization shows that this molecule has transparency in the visible range. To understand linear optical and microscopic second-order nonlinear optical (NLO) behavior of the compound, we have computed the electric dipole moment (mu) and dispersion-free first hyperpolarizabilities (beta) using Finite Field second-order MØller-Plesset perturbation (FF MP2) procedure; and also dispersion-free linear polarizabilities (alpha), frequency-dependent linear polarizabilities within the linear optical spectrum and first hyperpolarizabilities at lambda=730-1050 and 1000-1400 nm wavelength areas using time-dependent Hartree-Fock (TDHF) method. The ab-initio calculation results reveal that the examined complex might have linear optical and microscopic NLO behavior with non-zero values.

Scanning pyroelectric microscopy revealing the spatial polarity distribution in topologically centric crystals of trans-4-chloro-4′-nitrostilbene

Scanning pyroelectric microscopy (SPEM) was applied to investigate grown-in polarity in trans-4-chloro-4'-nitrostilbene (CNS) single crystals. Sectors {011} and {011} were scanned for cross sections perpendicular to the a-direction. A rotational analysis for {011}, {011} faces was performed for a needle like crystal turned around the a-axis. All pyroelectric experiments confirm a bipolar grown-in state of polarity for sector involving the twofold axis b. These measurements agree with theoretical force field and stochastic calculations, predicting a bipolar state and a nearly identical extent of polarity for two different sectors.

In situ diagnostics of the crystalline nature of single organic nanocrystals by nonlinear microscopy

We elucidate the crystalline nature and the three-dimensional orientation of isolated organic nanocrystals embedded in a sol-gel matrix, using a polarized nonlinear microscopy technique that combines two-photon fluorescence and second harmonic generation. This technique allows the distinction between monocrystalline structures and nanoscale polycrystalline aggregates responsible for incoherent second harmonic signals.