SERS spectroscopy study of merocyanine form of spironaphthoxazine derivatives

Merocyanine (MC) form of spironaphthoxazine (1) as well as its morpholine ( 2) and aza- 15-crown-5-ether (3) 6'-derivatives was studied by using the su rface-enhanced Raman scattering (SERS) spectroscopy. Characteristic bands w ere revealed that were sensitive to interactions of MC oxygen and to the co nfiguration of the molecule with respect to the =C-N= bridge between naphth alene and indolinic chromophores. The single isomer was detected for 1 and 1Eu(3+) complex in acetonitrile and for 1 in ethanol. It was ascribed to TT C (trans-trans-cis) form. Two isomers of 2 and 3 (TTC and CTC) coexisted in acetonitrile, ethanol and methanol, whereas CTC form was only present for 2 and 3 in 2,2.2-trifluoroethanol and fur complexes of 2 and 3 with metal c ations: (Ba2+, Mg2+, Eu3+) in acetonitrile. The MC oxygen of 2 and 3 was fo und to be protonated in 2,2,2-trifluoroethanol. (C) 2001 Elsevier Science B .V. All rights reserved.