Vibrational spectroscopy and DFT analysis of 4-cyanophenylhydrazine: A potential SERS probeMa, H (Ma, Hao); Liu, SL (Liu, Songlin); Zhu, L (Zhu, Lin); Ma, C (Ma, Chao); Han, XX (Han, Xiaoxia); He, CY (He, Chengyan); Zhao, B (Zhao, Bing)
Spectrochimia Acta Part A - Molecular and Biomolecular Spectroscopy, 2021, Volume 253, 119574
4-Cyanophenylhydrazine (4-CPH) is an organic synthesis intermediate. To date, several products derived from 4-CPH have been well studied; however, 4-CPH itself has not been extensively investigated. Herein, we performed vibrational and theoretical analyses of 4-CPH. Density functional theory (DFT) calculations were applied to predict the IR and Raman spectra of 4-CPH, which were compared with the experimental spectra. The calculated and experimental spectral results were in good agreement, except for an abnor-mal transformation of the protonated 4-CPH cyano group (C?N), which was observed in the theoretical IR spectrum. Several wavefunction analyses revealed that this transformation was due to the protonation-induced depolarization of the molecule. Moreover, we verified the applicability of 4-CPH as a probe for surface-enhanced Raman spectroscopy (SERS). We observed a pH-dependent shift in the cyano bond fre-quency within the silent region and determined, as a novel discovery, that this shift was induced by 4-CPH protonation. Our results provide considerable, fundamental information that confirms the potential of 4-CPH as a SERS probe. |
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