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NIR-FT Raman and FT-IR spectra of the crystallized 2,6-bis (p-N,N-dimethyl benzylidene)cyclohexanone (C 24 H 28 N 2 O) have been recorded in the region 3200-500 and 4000-400 cm −1 , respectively. The spectral interpretation has been done following full structure optimization and vibrational wavenumber calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G * basis set. The predicted vibrational spectra are in excellent agreement with the experiment, permitting an unambiguous assignment for the unusual downshifting of nC O caused by expanded conjugation effects in the dienone system. The optimized geometry clearly demonstrates the 'half-chair' conformation of the central nonheterocyclic ring. The ring C-H stretching vibrational modes involving aromatic hydrogen atoms participating in steric interaction have been observed with low intensities. There are valid structural and spectral bases for the enhancement of its bioactivity due to full charge transfer reaction by the substitution of the electron-donating 4-dimethylamino group into the aryl rings. The existence of intramolecular, C-H ... O, improper, blue-shifted hydrogen bond was investigated by means of the natural bonding orbitals (NBO) analysis. There are also slight dissimilarities in the bond lengths and endocyclic bond angles of both phenyl rings due to the effect of the heavy substitution. The characteristic ring modes have also been assigned in detail.

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.005 A Ê R factor = 0.057 wR factor = 0.141 Data-to-parameter ratio = 13.4For details of how these key indicators were automatically derived from the article, see

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-Key step in the synthesis of the title compounds is a regioselective 1,3-dipolar cycloaddition of bis(arylmethylidene)cyclohexanones to the azomethine ylide generated in situ from isatin and sarcosine.This method is expected to be valuable for the preparation of a variety of biologically important spiro(oxindole) derivatives.

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