Hydrothermal crystallisation of metal (II) orotates (M /nickel, cobalt, manganese or zinc). Effect of 2,2-bipyridyl, 2,2-dipyridyl amine, 1-methyl-3-(2-pyridyl)pyrazole, phenanthroline and 2,9- dimethyl-1,10-phenanthroline upon structure M. John Plater *, Mark R. St. J. Foreman, Janet M.S. Skakle, R. Alan Howie Department of Chemistry, University of Aberdeen, Room G103, Meston Building, Meston Walk, AB24 3UE Old Aberdeen, UK Received 16 July 2001; accepted 7 January 2002 Abstract Hydrothermal synthesis of orotic acid (H 3 L) with Ni(OAc) 2 × /4H 2 O gives a green 1D co-ordinative network of composition [Ni(HL)(H 2 O) 3 ](3). The kinetic product [Ni(HL) × /(H 2 O) 4 ]H 2 O(4) can be prepared by conventional crystallisation. When boiled in water it is transformed into the thermodynamically favoured trihydrate 3. An unstable blue phase 5 that could not be characterised was also observed. Hydrothermal synthesis of orotic acid and M(OAc) 2 × /4H 2 O (M/Ni, Co, Mn or Zn) and either 2,2-bipyridyl (bipy), 2,2-dipyridylamine (dpa), phenanthroline (phen), methyl-3-(2-pyridyl)pyrazole (pypz) or 2,9-dimethyl-1,10-phenanthroline (dmphen) gave infinite 1D co-ordinative networks of composition [M(HL)bipy(H 2 O)] (M/Co or Mn) (6  /7) and complexes of composition [Ni(HL)bipy (H 2 O) 2 ]2H 2 O (8); [Ni(HL)(dpa)(H 2 O) 2 ]H 2 O (9); [Ni(HL)(phen)(H 2 O) 2 ] × /2H 2 O (10); [Ni(HL)(C 9 H 9 N 3 )(H 2 O) 2 ] × /2H 2 O(11); [Ni(HL)(dmphen)(H 2 O)] (12); [Zn(HL)bipy(H 2 O)] (13) and [Ni(HL)(dpa) 2 ] × /0.5H 2 O(14). # 2002 Published by Elsevier Science B.V. Keywords: Hydrothermal; Coordination polymer 1. Introduction Metal  /ion complexes of orotic acid (1) and its substituted derivatives continue to attract attention because of its multidentate functionality and its pivotal role in bioinorganic chemistry [1]. It is a precursor in the biosynthesis of pyrimidine bases and nucleic acids in living organisms [2] and has been widely exploited in medicine. Its metal  /ion complexing properties are responsible for the successful application of orotate complexes in curing syndromes associated with defi- ciency of various metal ions [3]. It is an interesting multidentate ligand capable of coordinating to metal  / ions through the nitrogen atoms, the two carbonyl oxygens and the carboxylate oxygens. Existing studies of its coordination complexes demonstrate that it occurs as a dianion 2 coordinating often via the N1 atom and the carboxylic acid group so forming a five membered chelate ring. This leaves an ADA hydrogen bonding motif that can take part in supramolecular assembly and was recently shown to form a hydrogen bonding network with the DAD guest 2,6-diaminopyridine in the solid state [4]. Despite its polydentate nature only a few polymeric complexes of orotic acid have been observed. These include Co(III), [5] Ni(II) [5], and Mn(II) [6] complexes in which it acts as a tridentate ligand and bridges metal  /ions forming polymer chains. This paper reports our studies on the crystallisation of orotic acid metal  /ion complexes and an investigation into the effects of hydrogen bonding and metal  /ion coordination upon solid state architecture. Our previous studies have shown that co-crystallisation of benzene- 1,3,5-tricarboxylic and other polydentate acids with divalent metal ions in the presence of 2,2-bipyridyl (bipy), by hydrothermal synthesis, favours the forma- tion of porous 1D coordinative chains [7]. Bipy limits * Corresponding author. Tel.: 44-1224-272 943; fax: 44-1224- 272 921. E-mail address: m.j.plater@abdn.ac.uk (M.J. Plater). Inorganica Chimica Acta 332 (2002) 135  /145 www.elsevier.com/locate/ica 0020-1693/02/$ - see front matter # 2002 Published by Elsevier Science B.V. PII:S0020-1693(02)00728-4