Synthesis and spectral characterisation of new amido-ether Schiﬀ bases Oana Stamatoiu a, * , Alexej Bubnov b , Isabela T ß a ˆrcomnicu c , Mircea Iovu d a Faculty of Chemistry, University of Bucharest, 4-12 Regina Elisabeta Boulevard, 030018 Bucharest, Romania b Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague, Czech Republic c Pharma Serv International SRL, 52 Sabinelor Street, 050853 Bucharest, Romania d Faculty of Pharmacy, University of Medicine and Pharmacy, ‘‘Carol Davila’’, 2 Traian Vuia Street, 020956 Bucharest, Romania Received 27 August 2007; received in revised form 7 November 2007; accepted 9 November 2007 Available online 23 November 2007 Abstract Series of new compounds prepared by condensing the sodium salt of 4-[(4-methoxy-benzylidene)-amino]-phenol with chloro- acetanilides carrying various substituents in diﬀerent positions has been synthesised and characterised by UV–VIS, FTIR, MS, 1 H and 13 C NMR spectrometry. The eﬀect of type and position of diﬀerent substituents on thermal and on mesomorphic behaviour has been investigated by polarizing optical microscopy and diﬀerential scanning calorimetry studies. All compounds possess relatively high phase transition temperatures due to possibility of forming molecular associations and only the 2,4-substituted ones possess the liquid crystalline behaviour, namely the nematic phase. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Schiﬀ bases; Amido-ethers; Chloroacetanilides; Azomethine liquid crystals; Nematic phase 1. Introduction In our days, thermotropic liquid crystals are materials of great scientiﬁc and technological importance. The discovery of MBBA (4-methoxybenzylidene-4 0 -butyl- aniline), which exhibits a nematic phase at the room temperature, was a starting point for studies relating to the liquid crystalline behaviour of the Schiﬀ bases [1]. Until now Schiﬀ base esters with low molecular weight [2,3] have been investigated much more than the Schiﬀ base ethers. As it is known, the inﬂuence of a terminal alkyl chain upon the liquid crystalline properties [4,5] and the possibility of enhancing the rigidity of the Schiﬀ’s base core system through complexation [6–8] are two major pathways to improve the mesogenic properties [9]. Most of the Schiﬀ bases are p-substituted with long alkoxy chains but, a relatively small number with AOACH 2 AX terminal chain (where X represents everything else except an alkyl chain) are quoted [10–12]. Our present work focuses the attention both on synthesising a novel type of Schiﬀ base ethers in which the ether moiety is connected to an acetanilide group and on study the inﬂuence of various substituents carried by the acetanilide core on the physical, spectral, mesomorphic, and biological properties of the new compounds. Due to the existence of the amide group, in these structures the hydrogen bonding is a key interaction in the process of molecular aggregation and supramolecular architecture [13]. The mixing of H-bond donor and acceptor moieties can be expected to form a liquid crystalline hydrogen-bonded complex if the structure is designed properly [14]. On the other hand, previous studies [15,16] proved that if the hydrophilic amino group from the molecule of acetanilides, the best known being N-diethylamino- acetyl-2,6-dimethylaniline (lidocaine) [17], is substituted by aryloxy groups, the local anesthetic action remains as that of aminoacetanilides but the antiarrhythmic eﬀect is increasing. In this paper we report the synthesis, spectral characterisation, and mesomorphic properties of the azomethine-amido-ether series (13 compounds) with general 0022-2860/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2007.11.025 * Corresponding author. Tel.: +40 745 778099. E-mail address: oana_stam@yahoo.com (O. Stamatoiu). www.elsevier.com/locate/molstruc Available online at www.sciencedirect.com Journal of Molecular Structure 886 (2008) 187–196