Geometry Optimization and Second Harmonic Generation in Para-Nitroaniline–dimethyl Formamide Adduct

Abstract

Para-nitroaniline(p-NA)-dimethyl formamide (DMF) adduct has been synthesized chemically. The formation of adduct is confirmed via UV, FTIR, CHN analyses and other techniques. The adduct formation takes place due to dipolar interaction and hydrogen bonding. The parent polar molecules, viz. p-NA and DMF, crystallize in symmetric forms and do not exhibit optical second harmonic generation (SHG). The adduct has been found to exhibit a considerable SHG efficiency and hence this confirms that the adduct crystallizes in a noncentrosymmetric form. These observations suggest a Λ-shaped structure of the molecule, which is further established theoretically via geometry optimization.

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“…However, the CH 3 groups and CN of 3 o amines groups of DMNA molecules stretching vibration are observed at 2923 cm –1 and 1482 cm –129–31 in Figure 7(c). As for NO 2 , the asymmetric and symmetric stretching vibration of NO 2 group of these three nitroaniline compounds generally gives rise to bands in the regions 1500–1570 cm –1 and 1300–1370 cm –1 and the C–N stretch of NO 2 group is shown at 836 cm –1 21–30, 32…”

“…Figure 7 shows the FTIR spectra of nitroaniline compounds. The pNA FTIR spectrum show in Figure 7(a), the NH 2 of pNA molecules stretching vibration is observed at 3476 and 3360 cm –1 and the CN of 1 o amines groups stretch is observed at 1444 cm –1 21–24. Figure 7(b) shows the MNA FTIR spectrum.…”