The chemical reaction of 7-acetyl-6-hydroxy-3-mercapto-1,6-dimethyl-8-phenyl-5,6,7,8-tetrahydroisoquinoline-4-carbonitrile with N-(naphthalene-1-yl)-2-chloroacetamide in ethanol in the presence of anhydrous sodium acetate results in the synthesis of a 5,6,7,8-tetrahydroisoquinoline derivative with name 7-Acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-phenyl-3-[N-(naphthalen-1-yl)carbamoylmethylthio]-5,6,7,8-tetrahydroisoquinoline (ACCT). The synthesized compound is characterized by FT-IR, ¹H, and ¹³C NMR spectroscopy. Furthermore, the crystal structure is verified by single crystal X-ray diffraction (XRD), which shows that the molecular configuration of ACCT is stabilized by N─H … N bonding. Infinite C(11) molecular chains are formed by O─H … O bonding that runs along the b-axis, and consecutive chains are further interlinked by C─H … O bonding. Hirshfeld surface analysis reveals the role of intermolecular interaction in crystal packing, where H … H and C—H … O interactions have notable percentage contributions. Dispersioninteractions provides the dominant stabilization for supramolecular assembly, followed in significance by electrostatic interactions. Electronic structure calculations and aromaticity analysis reveal the reactivity of the synthesized compound at the M062x/def2tzvp method. With the help of DFT simulations, the crucial role of van der Waals forces and charge transfer in modifying optical and non-linear optical (NLO) properties has been underscored. Ab initio molecular dynamics study reveals the thermodynamic and kinetic behavior at room temperature.