Electron Donor and Acceptor Influence on the Nonlinear Optical Response of Diacetylene-Functionalized Organic Materials (DFOMs): Density Functional Theory Calculations

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.

Exploring the Franck–Condon region of a photoexcited charge transfer complex in solution to interpret femtosecond stimulated Raman spectroscopy: excited state electronic structure methods to unveil non-radiative pathways

“…Weak D-A complexes have attracted interest since the discovery of the conductive metal-like properties of the tetrathiafulvalene-tetracyanoquinodimethane complex in the early seventies [21][22][23][24][25] and recently they have regained popularity due to their versatility in a wide range of elds such as organic opto-electronics, 26 solar energy conversion [27][28][29][30] and non-linear spectroscopy. [31][32][33] According to Mulliken D-p-A complex theory, 34,35 a CT complex is composed of two independent subunits forming a non-covalent dimer with an acid-base Lewis character, and thus a partial donation of electronic density stabilizes the dimer formation giving rise to mutual Coulomb interactions. When in solution, the complexation leads to a small charge transfer which strongly increases upon photoexcitation generating a CT state (D r+ /A rÀ ), whose electronic density rearranges faster compared to the nuclear motion in a very different manner with respect to the ground state one.…”

A Theoretical Perspective on Strategies for Modeling High Performance Nonlinear Optical Materials

“…The involvement of extended conjugation and charge transfer character have been explored via different DFT methods. The enhanced NLO response (β ̥ 2.5×10 4 au) of the designed diacetylene-functionalized organic complexes reflected that these complexes could serve as better NLO candidates (Khalid et al, 2019). The development of novel synthetic and theoretical techniques leads to more diverse substitution patterns of porphyrin rings because it widens the potential applicability in nonlinear optics.…”

Synthesis of Diaminopyrimidine Sulfonate Derivatives and Exploration of Their Structural and Quantum Chemical Insights via SC-XRD and the DFT Approach

“… 14 Recently, our research group published reports on the quantum chemical designing and modifications of π-linkers and donor and acceptor groups of chemical structures of organic compounds. 15 Also, very recently our research group has reported that O -benzenesulfonylated pyrimidines possess promising NLO properties. 16 Herein, our results on the synthesis, structural exploration with the help of single-crystal X-ray diffraction (SC-XRD) analysis, and comprehensive computational analysis of crystalline organic compounds, i.e., 2,6-diaminopyrimidin-4-yl naphthalene-2-sulfonate ( A ) and 2,6-diaminopyrimidin-4-yl 4-methylbenzenesulfonate ( B ), are given.…”