Synthesis, crystal growth and characterization of organic nonlinear optical materials methoxy-N,N-diphenylbenzamides

Organic NLO materials, 2-methoxy- N , N -diphenylbenzamide (2MNNDPB), 4-Methoxy- N , N -diphenylbenzamide (4MNNDPB) and 3-methoxy- N , N -diphenylbenzamide (3MNNDPB), were synthesized by benzoylation of N , N -diphenylamine with methoxy substituted benzoyl chlorides. The single crystals of 2MNNDPB (3a) , 3MNNDPB (3b) and 4MNNDPB (3c) were grown by a slow evaporation method in a dimethyl sulfoxide solvent. The X-ray diffraction shows that 2MNNDPB, 3MNNDPB and 4MNNDPB crystals belong to triclinic, orthorhombic and monoclinic crystallographic systems with space groups Pbca, P-1 and P2 1 /n, respectively. FTIR spectra revealed the various functional groups and the chemical bonding, with the amide carbonyl peak appearing at 1658, 1649 and 1656 cm −1 in 2MNNDPB, 3MNNDPB and 4MNNDPB, respectively, and also confirmed by NMR spectra ( 1 H and 13 C) the number of protons and carbons present in the synthesized materials. UV–Vis spectra show 67%, 59% and 72% transmission in the visible region of the 2MNNDPB, 3MNNDPB and 4MNNDPB crystals. TGA/DTA analysis revealed that the 2MNNDPB, 3MNNDPB and 4MNNDPB crystals were thermally stable up to 354 K, 402 K, and 418 K, respectively. The second harmonic generation (SHG) of 2MNNDPB (3a) , 3MNNDPB (3b) and 4MNNDPB (3c) crystals was determined by Kurtz–Perry powder method and found that 2.3, 2.7 and 2.2 times higher than that of KDP crystal.