Abstract
High-tech electronic, optics, and storage devices require organic compounds with nonlinear optical (NLO) properties. This study designed D-π-A based dyes with donor triphenylamine (TPA) and acceptor dicyanovinylene (DCV) species by structurally modifying π-conjugated linkers. Our density functional theory (DFT) computations analyzed the impact of structural variations on the nonlinear optical (NLO) response of newly designed dyes. The B3LYP/6-31G(d,p) level determined the quantic chemical insights: frontier molecular orbital (FMOs), natural bond orbitals (NBOs), and nonlinear optical (NLO) properties of the designed dyes (DPTM-1 to DPTM-12). UV-Vis analysis based on the TD-DFT/CAM-B3LYP/6-311+G(d,p) level explored the optoelectronic properties. DPTM-1 and DPTM-5 showed the highest red-shifted absorption band at 519 and 506 nm. NBO analysis shows that DPTM-1 to DPTM-12 dyes have positive values for all donors (D) and π-spacers but negative values for acceptors (A). The π-spacers act as a conveyer between donor and acceptor moieties; thus, electrons were transferred smoothly from D to A units, which resulted in a charge separation state. Our calculations show the extent of NLO response in terms of electronic transitions, polarizability <α>, and first hyperpolarizability (β) values. The highest value of βtotal was 110,509.23 a.u. manifested in DPTM-6 due to 2,5-dimethyloxazole as a second π-linker, twice that of R (66,275.95 a.u.). Also, DPTM-6 and DPTM-8 exhibit the lowest energy band gap of 2.06 and 2.04 eV, respectively. In short, all DPTM-1 to DPTM-12 dyes manifested maximum absorption, lowest energy band gap, greater charge transfer from donor to the acceptor, and better first hyperpolarizability values as compared to the R and showed good NLO response. The present work represents new compounds with remarkable NLO properties and their applications in modern high-tech devices.
Highlights
With the rapid rise of high-tech electronic, optics, and storage devices, organic compounds with NONLINEAR OPTICAL (NLO) properties gained unparalleled popularity and dominance in various disciplines, such as medicine, material science, atomic, molecular, and solidstate physics, surface interface sciences, and chemical dynamics (Eaton, 1991; Peng and Yu, 1994; Tsutsumi et al, 1998; Breitung et al, 2000; Christodoulides et al, 2010)
The objective of the present study was to investigate NLO properties of metal-free, theoretically designed organic dyes (DPTM-1 to DPTM-12) comprising of various π-linkers mixed with D and A
To elucidate the impact of various π-bridges on NLO properties, TDDFT and density functional theory (DFT) methods have been employed on designed dyes (DPTM-1 to DPTM-12)
Summary
With the rapid rise of high-tech electronic, optics, and storage devices, organic compounds with NLO properties gained unparalleled popularity and dominance in various disciplines, such as medicine, material science, atomic, molecular, and solidstate physics, surface interface sciences, and chemical dynamics (Eaton, 1991; Peng and Yu, 1994; Tsutsumi et al, 1998; Breitung et al, 2000; Christodoulides et al, 2010). A significant amount of NLO responses has been observed in organic compounds due to π-electrons with strong electric polarization, low dielectric coefficient, quick response, and high laser damage threshold and π-bond system involves charge distribution from donor to acceptor (Sung and Hsu, 1998; Hochberg et al, 2006). Appropriate arrangement of donor, acceptors, and π-bridge plays a crucial role in designing a competent organic compound (Dalton, 2001; Dalton, 2002). This appropriate arrangement enhances the electronic distribution, induces charge separation, increases absorption range towards longer wavelength, reduces charge recombination, and decreases the HOMO-LUMO energy gap, resulting in an improved NLO response. Different types of π-spacers are helpful in a good connection between HOMO and LUMO units to have a good NLO response (Khan et al, 2018a)
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