Acceptor-driven synergy in dihydropyridine-based compounds reveals giant static and frequency-dependent hyperpolarizabilities: a quantum exploration

Abstract

Dihydropyridine carbonitrile derivatives exhibit strong nonlinear optical (NLO) performance due to efficient charge-transfer properties, making them promising for optical applications. In current study, dihydropyridine carbonitrile based compounds (CTP1–CTP6) were designed by structural modeling of reference compound (CTPR) with malononitrile-based acceptors for utilization as NLO materials. All quantum chemical calculations were performed via DFT and TD-DFT methods at the M06/6-311G(d,p) level of theory. The designed molecules have donor–π–acceptor (D–π–A) framework, and this push–pull archiecture was improved by the introduction of electron-withdrawing moiety on acceptors. FMO analysis revealed small energy gaps and effective charge transfer from donor to acceptor regions. The absorbance maxima varied from 412 to 584 nm, indicating a redshift in optical behavior. The significant NLO properties were investigated in CTP4, including average polarizability (1.443 × 10⁻²² esu), first-order hyperpolarizability (9.279 × 10⁻²⁸ esu), and second hyperpolarizability (4.231 × 10⁻³³ esu), owing to its good optoelectronic properties. The first hyperpolarizability shows a remarkable enhancement, with a maximum value of 9.279 × 10⁻²⁸ esu (CTP4), which is nearly 10²–10³ times higher than that of para-nitroaniline (p-NA), the standard reference compound. These findings qualitatively indicate that structural modification can greatly enhance the charge-transfer efficiency and quantitatively make the studied systems promising for high-performance optoelectronic and photonic applications.