Abstract
Herein, we report the quantum chemical results based on density functional theory for the polarizability (α) and first hyperpolarizability (β) values of diacetylene-functionalized organic molecules (DFOM) containing an electron acceptor (A) unit in the form of nitro group and electron donor (D) unit in the form of amino group. Six DFOM 1–6 have been designed by structural tailoring of the synthesized chromophore 4,4′-(buta-1,3-diyne-1,4-diyl) dianiline (R) and the influence of the D and A moieties on α and β was explored. Ground state geometries, HOMO-LUMO energies, and natural bond orbital (NBO) analysis of all DFOM (R and 1–6) were explored through B3LYP level of DFT and 6-31G(d,p) basis set. The polarizability (α), first hyperpolarizability (β) values were computed using B3LYP (gas phase), CAM-B3LYP (gas phase), CAM-B3LYP (solvent DMSO) methods and 6-31G(d,p) basis set combination. UV-Visible analysis was performed at CAM-B3LYP/6-31G(d,p) level of theory. Results illustrated that much reduced energy gap in the range of 2.212–2.809 eV was observed in designed DFOM 1–6 as compared to parent molecule R (4.405 eV). Designed DFOM (except for 2 and 4) were found red shifted compared to parent molecule R. An absorption at longer wavelength was observed for 6 with 371.46 nm. NBO analysis confirmed the involvement of extended conjugation and as well as charge transfer character towards the promising NLO response and red shift of molecules under study. Overall, compound 6 displayed large <α> and βtot, computed to be 333.40 (a.u.) (B3LYP gas), 302.38 (a.u.) (CAM-B3LYP gas), 380.46 (a.u.) (CAM-B3LYP solvent) and 24708.79 (a.u.), 11841.93 (a.u.), 25053.32 (a.u.) measured from B3LYP (gas), CAM-B3LYP (gas) and CAM-B3LYP (DMSO) methods respectively. This investigation provides a theoretical framework for conversion of centrosymmetric molecules into non-centrosymmetric architectures to discover NLO candidates for modern hi-tech applications.
Highlights
In recent years, organic nonlinear optical (NLO) materials have been the focus of intense research because of their promising functions in the field of optoelectronic technologies for signal processing, optical switching, telecommunication and information storage [1,2,3]
NLO properties of materials are governed by intramolecular charge transfer (ICT) which mainly originates from donor (D) to acceptor (A) moieties via π-conjugated bridges [4,5,6,7]
density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were performed for the estimation of electronic structures, absorption spectra and NLO properties of the diacetylene-based compounds
Summary
Organic nonlinear optical (NLO) materials have been the focus of intense research because of their promising functions in the field of optoelectronic technologies for signal processing, optical switching, telecommunication and information storage [1,2,3]. The reasons for the focus of organic compounds involves their facile synthesis, low cost, and structural tailoring which enables the chemical tuning of their structures for desired NLO properties. The design of high performance NLO materials involves appropriate donor-π-conjugated bridge-acceptor (D-π-A) systems that can be tailored through structural modification of the π-conjugated bridge, D or A substituents [8,9,10,11,12,13,14,15,16,17]. Polymers and small molecules having diacetylene moieties in their backbone have been widely explored [21]. For these reasons, huge efforts have been made to suggest extremely valuable diacetylene functionalized organic materials (DFOMs) for hi-tech applications
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