Unveiling the NLO Potential of New Zn (II) Complex of 6‐Methylpyridine‐2‐Carboxaldehyde: Experimental/DFT Study on Spectral, Static, and Frequency‐Dependent Linear/Nonlinear Optical Parameters

ABSTRACT Ongoing exploration focuses on synthesizing and characterizing coordination compounds to improve the design of nonlinear optical (NLO)‐based materials. In this regard, to examine spectral and static/frequency–dependent linear/NLO parameters, the new Zn (II) complex {[Zn(6‐MePyAld) 2 (Cl)]; 6‐MePyAld: 6‐methylpyridine‐2‐carboxaldehyde} was synthesized and characterized by using 1 H and 13 C NMR, mass (LC‐HRMS), powder XRD, and FTIR spectra. The electronic features of synthesized complex were investigated by considering the TD‐CAM‐B3LYP/ and TD‐M06L/6‐311G(d,p)//LanL2DZ levels of time‐dependent density functional theory (TD‐DFT). Moreover, the theoretical linear optical (LO), second‐, and third‐order NLO susceptibility tensors/polarization ( χ (1) / P (1) , χ (2) / P (2) , χ (3) / P (3) ) parameters for the Zn (II) complex were computed using the DFT/M06L and DFT/CAM‐B3LYP levels. The external electric field ( E ), polarization ( P ), and electric displacement ( D ) values of the Zn (II) complex were also calculated using the same DFT levels. To investigate microscopic LO (isotropic polarizability < α (0;0)>/< α (− ω ; ω )>, and anisotropic polarizability ( ∆α (0;0)/ ∆α (− ω ; ω )) and second‐/third‐order NLO (< β (0;0,0)>/< β (− ω ; ω ,0), < β (−2 ω ; ω , ω )>/< γ (0;0,0,0)>/< γ (− ω ; ω ,0,0)> and < γ (−2 ω ; ω , ω ,0)>) parameters for the Zn (II) complex, the DFT/M06L and DFT/CAM‐B3LYP levels in the gas phase were used. The ∆α (0;0), ∆α (− ω ; ω ), < β (0;0,0)>, < β (− ω ; ω ,0)>, and < β (−2 ω ; ω , ω )> for Zn (II) complex were computed at 17.288 × 10 −24 , 21.782 × 10 −24 , 14.692 × 10 −30 , 466.80 × 10 −30 , and 210.79 × 10 −30 esu, respectively, by using the DFT/CAM‐B3LYP level. Moreover, the < γ (0;0,0,0)>/< γ (− ω ; ω ,0,0)> and < γ (−2 ω ; ω , ω ,0)> in the gas phase computed at the DFT/CAM‐B3LYP level for Zn (II) complex were obtained at 129.74 × 10 −36 , 3997.6 × 10 −36 , and −886.60 × 10 −36 esu, in turn. According to the CAM‐B3LYP level, the < γ (0;0,0,0)> value is 8.65 and 18.53 times higher than the values of para ‐nitroaniline (pNA) and urea, respectively. The obtained static/dynamic β and γ values of Zn (II) complex are greater than those of urea and pNA. Zn (II) complex exhibited remarkably microscopic second‐order and particularly third‐order NLO features. It is predicted that our study will shed light on NLO materials that might be used in telecommunication and optoelectronics.