Crystal Structure And Theoretical Studies Of The Keto-enol Isomerism Of N,n′-bis(salicylidene)-o-phenylenediamine (salophen)

The Schiff base N,N′-bis(salicylidene)-o-phenylenediamine (salophen) was prepared by the condensation of salicylaldehyde with o-phenylenediamine in ethanol solution. The compound was characterized by elemental analysis, infrared (IR), 1H, 13C and 1H15N HMBC nuclear magnetic resonance (NMR) spectroscopic measurements, and also by X-ray diffraction. The tautomerism of salophen was also studied by calculations using density functional theory (DFT). Two of the three tautomers were shown to coexist. A comparison of the DFT data of the three tautomers has shown that the most stable one is salophen 1, which is in accordance with experimental X-ray crystallographic data. © 2012 Published by Elsevier B.V.99110115Sessler, J.L., Melfi, P.J., Pantos, G.D., (2006) Coord. Chem. Rev., 250, pp. 816-843Calil, N.O., De Carvalho, G.S.G., Franco, D.C.Z., Da Silva, A.D., Raposo, N.R.B., (2012) Lett. Drug Des. Discov., 9, pp. 8-11Pavan, F.R., Carvalho, G.S.G., Silva, A.D., Leite, C.Q.F., (2011) Sci. World J., 11, pp. 1113-1119Liu, J., Zhang, B., Wu, B., Zhang, K., Hu, S., (2007) Turk. J. Chem., 31, pp. 623-629Kandhar, A.A., Shaabani, B., Belaj, F., Bakhtiari, A., (2007) Inorg. Chim. Acta, 360, pp. 3255-3264McQuate, R.S., Leussing, D.L., (1975) J. Am. Chem. Soc., 97, pp. 5117-5125Lloret, F., Mollar, M., Faus, J., Julve, M., Castro, I., Diaz, W., (1991) Inorg. Chim. Acta, 189, pp. 195-206Türkoglu, G., Berber, H., Dal, H., Ögretir, C., (2011) Spectrochim. Acta Part A, 79, pp. 1573-1583Trzesowska-Kruszynska, A., (2010) Struct. Chem., 21, pp. 131-138Sliznev, V.V., Girichev, G.V., (2011) J. Struct. Chem., 52, pp. 16-26CrysAlis RED, , Oxford Diffraction Ltd., Version 1.171.32.38 (release 17-11-2008 315 CrysAlis171.NET) (compiled November 17 2008, 13:58:09)Sheldrick, G.M., (1997) SHELXL-97 - A Program for Crystal Structure Refinement, , GermanyFarrugia, L.J., (1997) J. Appl. Cryst., 30. , 565-565Schmidt, M.W., Baldridge, K.K., Boatz, J.A., Elbert, S.T., Gordon, M.S., Jensen, J.H., Matsunaga, S.K.N., Montgomery Jr., J.A., (1993) J. Comput. Chem., 14, pp. 1347-1363Ditchfie, R., Hehre, W.J., Pople, J.A., (1971) J. Chem. Phys., 54, pp. 724-728Francl, M.M., Pietro, W.J., Hehre, W.J., Binkley, J.S., Gordon, M.S., Defrees, D.J., Pople, J.A., (1982) J. Chem. Phys., 77, pp. 3654-3665Harihara, P.C., Pople, J.A., (1973) Theor. Chim. Acta, 28, pp. 213-222Hehre, W.J., Ditchfie, R., Pople, J.A., (1972) J. Chem. Phys., 56, pp. 2257-2261Becke, A.D., (1993) J. Chem. Phys., 98, pp. 5648-5652Lee, C.T., Yang, W.T., Parr, R.G., (1988) Phys. Rev. B, 37, pp. 785-789Miertus, S., Scrocco, E., Tomasi, J., (1981) Chem. Phys., 55, pp. 117-129Scott, A.P., Radom, L., (1996) J. Phys. Chem., 100, pp. 16502-16513Schaftenaar, G., Noordik, J.H., (2000) J. Comput. - Aided Mol. Des., 14, pp. 123-134Chizhov, D.L., Khmara, E.F., Slepukhin, P.A., Filyakova, V.I., Charushin, V.N., (2010) J Struct. Chem., 51, pp. 288-295Flores-Leonar, M., Esturau-Escofet, N., Méndez-Stivalet, J.M., Marín-Becerra, A., Amador-Bedolla, C., (2011) J. Mol. Struct., 1006, pp. 600-605Zavodnik, V.E., Bel'Skii, V.K., Zorkii, P.M., (1987) J. Struct. Chem., 28, pp. 175-177Fukuyo, M., Hirotsu, K., Higuchi, T., (1982) Acta Cryst., 38 B, pp. 640-643Pereira, G.A., Massabni, A.C., Castellano, E.E., Sodre-Costa, L.A.S., Leite, C.Q.F., Pavan, F.R., Cuin, A., (2012) Polyhedron, 38, pp. 291-29