“…Its electrochemical (Leventis et al, 2004a,b) and host/guest (Rawashdeh et al, 2008) characteristics have already been reported earlier. However, considering research on the behaviour in the crystal state, only 4-benzoylpyridine as a mother compound was described so far in complexes with transition metals (Araki et al, 2005;Mautner & Gohera, 1998;Gohera & Mak, 1998;Escuer et al, 2000;Gohera & Mautner, 1999;Drew et al, 1985;Gotsis & White, 1987) as well as in co-crystals with various benzoic acids (Sugiyama et al, 2002a,b) and being derivatized with chlorine in the para position of the benzene ring (Syed et al, 1984). Structural studies on the respective benzoyl-pyridinium species are rather rare both featuring a squaric acid group at the nitrogen atom (Kolev et al, 2001;Kolev et al, 2005).…”