Vibrational spectroscopic investigations of 5-(4-¯uor-phenyl)-furan-2 carbaldehyde T. Iliescu a,* , F.D. Irimie b , M. Bolboaca c , Cs. Paisz b , W. Kiefer c a Babes Ë-Bolyai University, Physics Department, 3400 Cluj-Napoca, Romania b Babes Ë-Bolyai University, Chemistry Department, 3400 Cluj-Napoca, Romania c Institut fu Èr Physikalische Chemie, Universita Èt Wu Èrzburg, D-97074 Wu Èrzburg, Germany Received 31 August 2001; accepted 23 October 2001 Abstract Infrared and FT-Raman spectra of 5-(4-¯uor-phenyl)-furan-2 carbaldehyde were recorded and analyzed. Density functional theory (DFT) calculations were performed for the two rotational isomers, the anti-form isomer being more stable than syn-form isomer by 808.65 J mol 1 . # 2002 Elsevier Science B.V. All rights reserved. Keywords: Raman spectroscopy; DFT calculations; Furan-2 carbaldehyde derivatives 1. Introduction Furan-2 carbaldehyde derivatives are very impor- tant intermediates in organic synthesis. The bacterio- static effects of these compounds were checked-up with good results. The action of many drugs is determined by their structure. In the present study, we performed the investigation of the two rotational isomers of 5-(4-¯uor-phenyl)-furan-2 carbaldehyde (5-(4FP)-F-2C) from an analytical (infrared and FT-Raman spectroscopy) and theoretical (DFT calcu- lations) point of view. To our knowledge, these data are not yet present in the literature. 2. Experimental The compound was obtained from the corre- sponding diazonium salt and furfural in aqueous medium using CuCl 2 catalyst [1]. The product was puri®ed with column chromatography on silica gel. The FT-Raman spectra were recorded using a Bruker IFS 120HR spectrometer with an integrated FRA 106 Raman module and a resolution of 2 cm 1 . Radiation of 1064nm from a Nd-YAG laser was employed for excitation. A Ge detector, cooled with liquid nitrogen, was used. The infrared spectra, in KBr pellets, were recorded with a Bruker IFS 25 spectro- meter and a resolution of 2 cm 1 . Density functional theory (DFT) calculations were performed using Gaussian 98 [2]. All calculations of harmonic wavenumbers were performed using fully optimized geometry as reference geometry. The DFT geometry optimization was carried out with the com- bination of Becke's 1988 exchange functional [3] and Perdew±Wang 91 gradient-corrected correlation func- tional [4] (BPW91). The 6-311  G  basis set for all atoms has been employed in the geometry optimiza- tion and the vibration calculations. Vibrational Spectroscopy 29 (2002) 235±239 * Corresponding author. E-mail address: ilitra@phys.ubbcluj.ro (T. Iliescu). 0924-2031/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0924-2031(01)00182-5