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Abstract: Metal ions play a key role in nucleic acid structure and activity. The elucidation of factors/rules that govern the binding of metal ions is therefore an essential step for the better understanding of nucleic acid functions. In this review, we deal with stereospecific intra-molecular interligand interactions as such a factor, involving hydrogen-bonding, electrostatic interaction, and steric constraints, especially focusing on their significance as a factor that could affect base-specific metal bonding to adenine and guanine bases in the solid state. [Copyright &y& Elsevier]

Abstract: Reaction of tris(2-aminoethyl)amine (tren) and Cu(ClO4)2, Ni(ClO4)2, or Ni(NO3)2 with purine nucleobases (adenine, 9-ethylguanine, and hypoxanthine) gave five ternary tren–metal ion–nucleobase complexes, [Ni(tren)(adeninato)(ClO4)]·adenine (1), [Cu(tren)(9-ethylguanine)]·(ClO4)2 (2), [{Ni(tren)(H2O)}2(hypoxanthinato)]·(ClO4)3 ·1.5H2O (3), [Ni(tren)(hypoxanthinato)(H2O)]·ClO4 ·2H2O (4), and [{Ni(tren)(H2O)}2(hypoxanthinato)]2 ·(NO3)6 ·4.5H2O (5), where 1 and 4 were prepared under pH 8–9 while 2, 3, and 5 were under pH 6–7, and their crystal structures were determined by X-ray diffraction. In the adenine complex 1, the tren-capped metal ion binds to the base through N(9) with the formation of an intramolecular interligand hydrogen bond between the amino group of tren and N(3) of the base, and the 9-ethylguanine complex 2 involves the metal bonding to N(7) of the base with the formation of an intramolecular hydrogen bond between the amino group of tren and O(6) of the base. In the hypoxanthine complexes 3 and 5, the metal ions bind to N(7) in addition to N(9), forming three intramolecular hydrogen bonds, two involving O(6) with the amino nitrogen of tren and the aqua ligand and one between the aqua ligand and N(3) of the base, whereas the hypoxanthine complex 4 involves the metal bonding solely to N(9) with the formation of an intramolecular hydrogen bond between the aqua ligand and N(3) of the base, where N(7) as well as N(1) are hemi-protonated. The absence of the metal–N(7) bonding for adenine in 1 while the metal bonding to N(7) specific for guanine derivatives in 2, 3 and 5 are rationalized in terms of interligand interactions. [Copyright &y& Elsevier]

The reaction of VO(ph-acac)2 (ph-acac=phenyacetylacetonato) with NaHB(pz)3 (pz=pyrazole) or NaHB(3,5-Me2pz)3 in the solution of MeOH gave oxovanadium (IV) complexes HB(pz)3VO(ph-acac) · 2H2O (1) and HB(3,5-Me2pz)3VO(ph-acac) · 2H2O (2), respectively. An oxovanadium complex, V2O4[HB(pz)3]2 · 2CH3CN (3), was obtained by the reaction of VOSO4 · 3H2O with tri(pyrazolyl)borate sodium in MeOH. The complexes 1, 2 and 3 were characterized by elemental analysis, IR, UV-Vis, NMR. In particular, the crystals of complex 1 and 3 were determined by X-ray diffraction. They crystallize in space group P21/c, a=16.497(5) Å, b=7.6601(19) Å, c=17.199(4) Å, β=107.498(19)°, V=2072.8(9) Å3, Z=4, R=0.0371 (I>2σ(I)) for 1; in the monoclinic, space group Pbca, with cell dimensions of a=15.531(2) Å; b=18.007(2) Å; c=10.725(2) Å; V=2999.4(8) Å3, Z=4, R= 0.0401(I>2σ(I)) for 3. Structure analyses have shown that complex 1 is a monomeric oxovanadium complexe containing polypyrazolylborate and two lattice water. Complex 3 consists of a V2O4(HB(pz)3)2 molecule and two free CH3CN lattice molecules in an unit cell. Both possess a similar coordination mode for the vanadium atom. In addition, luminescence properties and thermal analysis characterization of the complexes also are discussed. [ABSTRACT FROM AUTHOR]

An investigation into the interactions between thiamine monophosphate (TMP) and anions has resulted in the preparation and X-ray characterization of the compounds (TMP)(Hg2Br5)·0.5H2O (1) and (TMP)2(Hg3I8) (2). In each compound the TMP molecule exists as a monovalent cation in the usual F conformation. The halogenomercurate anions occur in two-dimensional (2-D) network in 1 or one-dimensional (1-D) chain in 2. In both 1 and 2, the structures consist of alternating cationic sheets of the hydrogen-bonded TMP molecules and anionic sheets of the polymeric halogenomercurate anions. The TMP molecule binds to the polymeric anions through the characteristic ‘anion bridge I’, C(2)&z.sbnd;H⋯X⋯pyrimidinium (X=Br in 1 and I in 2), and electrostatic interactions between electropositive S(1) and halogen atoms. The ‘anion bridge II’ of the type N(4′1)&z.sbnd;H⋯X⋯thiazolium (X=phosphate group) plays a role in stabilizing the molecular conformation. The biological implication of the host–guest-like complexation between TMP and polymeric anions is discussed. [Copyright &y& Elsevier]

Abstract: Reaction of 1,4,7,10-tetraazacyclododecane (cyclen) and Cu(ClO4)2·6H2O with nucleobases (adenine, hypoxanthine, xanthine, theophylline, cytosine, or uracil) under alkaline conditions gave four ternary cyclen–metal–nucleobase complexes, [Cu(cyclen)(adeninato)]·ClO4·2H2O (1), [{Cu(cyclen)}2(hypoxanthinato)]·(ClO4)3 (2), [Cu(cyclen)(theophyllinato)]3·(ClO4)3·2H2O (3), and [Cu(cyclen)(xanthinato)]·(0.7ClO4)·(0.3ClO4)·3H2O·(0.5H2O)3 (4), whose crystal structures were determined by X-ray diffraction. In the adenine complex 1, a cyclen-capped square–pyramidal Cu2+ ion binds to an adeninato ligand through N(9) with the formation of an intramolecular interligand hydrogen bond between the secondary amino nitrogen of cyclen and N(3) of the base. In the hypoxanthine complex 2, two cyclen-capped Cu2+ ions bind to a hypoxanthinato ligand, one through N(7) with the formation of an intramolecular N(cyclen)–H···O(6) hydrogen bond and the other through N(9) to form an intramolecular N(cyclen)–H···N(3) hydrogen bond. Similarly, in both the theophylline complex 3 and the xanthine complex 4, each cyclen-capped Cu2+ ion binds to a theophyllinato or xanthinato ligand through N(7) with the formation of an intramolecular N(cyclen)–H···O(6) hydrogen bond. However, unlike in 2, steric constraints between amino group(s) of cyclen and the methyl group at N(3) of theophylline in 3 or the proton attached to N(9) of xanthine in 4 preclude the metal bonding to N(9) in 3 or N(3) in 4. The significance of intramolecular interligand interaction as a factor that affects metal-binding site(s) on nucleobases is emphasized. [Copyright &y& Elsevier]

Abstract: Reaction between nucleobases (adenine, hypoxanthine, cytosine, and uracil), tris(2-aminoethyl)amine (tren) and M(ClO4)2 (M2+ =Zn2+, Cd2+, Ni2+ or Cu2+) under pH 8–9 gave eight ternary tren-metal ion-nucleobase complexes, among which seven crystal structures, [Zn(tren)(adeninato)]·ClO4 (1), [Cd(tren)(adeninato)]·ClO4 (2), [Ni(tren)(adeninato)(ClO4)] (3), [Zn(tren)(hypoxanthinato)]·ClO4 ·H2O (4), [{Cd(tren)}2(hypoxanthinato)]·(ClO4)3 ·0.5 H2O (5), [Ni(tren)(uracilato)(H2O)]·ClO4 ·(0.5H2O)2 (7), and [Cu(tren)(uracilato)]·ClO4 ·0.5H2O (8) were determined by X-ray diffraction. In each of the adenine complexes with Zn2+ (1), Cd2+ (2), and Ni2+ (3), among which 1 and 2 are isostructural to each other, a tren-capped metal ion binds to an adeninato ligand through N(9) with the formation of an intramolecular interligand hydrogen bond between the amino nitrogen of tren and N(3) of the base. In the hypoxanthine complexes 4 and 5, a tren-capped Zn2+ ion in 4 binds to a hypoxanthinato ligand through N(9) with the formation of an intramolecular N(tren)–H⋯N(3) hydrogen bond, while in 5 two tren-capped Cd2+ ions bind to a hypoxanthinato ligand, one through N(7) with the formation of an intramolecular N(tren)–H⋯O(6) hydrogen bond and the other through N(9) to form an intramolecular N(tren)–H⋯N(3) hydrogen bond. In each of the uracil complexes with Ni2+ (7) and Cu2+ (8), a tren-capped metal ion binds to an uracilato ligand through N(1) with the formation of an intracomplex O(aqua)–H⋯O(2) hydrogen bond in 7 or an intramolecular N(tren)–H⋯O(2) hydrogen bond in 8. Tren-capped metal ion-bonded nucleobases act as building blocks for the assembly of supramolecular structures, by versatile hydrogen bonding and/or stacking abilities of nucleobases. The significance of intramolecular interligand interaction as a factor that affects metal-binding site(s) on nucleobases is emphasized. [Copyright &y& Elsevier]