Karthikeyan Ammasai, Zeller Matthias, Thomas Muthiah Packianathan
School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamilnadu, India.
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA.
Acta Crystallogr C Struct Chem. 2018 Jul 1;74(Pt 7):789-796. doi: 10.1107/S2053229618007672. Epub 2018 Jun 5.
Three new metal(II)-cytosine (Cy)/5-fluorocytosine (5FC) complexes, namely bis(4-amino-1,2-dihydropyrimidin-2-one-κN)diiodidocadmium(II) or bis(cytosine)diiodidocadmium(II), [CdI(CHNO)], (I), bis(4-amino-1,2-dihydropyrimidin-2-one-κN)bis(nitrato-κO,O')cadmium(II) or bis(cytosine)bis(nitrato)cadmium(II), [Cd(NO)(CHNO)], (II), and (6-amino-5-fluoro-1,2-dihydropyrimidin-2-one-κN)aquadibromidozinc(II)-6-amino-5-fluoro-1,2-dihydropyrimidin-2-one (1/1) or (6-amino-5-fluorocytosine)aquadibromidozinc(II)-4-amino-5-fluorocytosine (1/1), [ZnBr(CHFNO)(HO)]·CHFNO, (III), have been synthesized and characterized by single-crystal X-ray diffraction. In complex (I), the Cd ion is coordinated to two iodide ions and the endocyclic N atoms of the two cytosine molecules, leading to a distorted tetrahedral geometry. The structure is isotypic with [CdBr(CHNO)] [Muthiah et al. (2001). Acta Cryst. E57, m558-m560]. In compound (II), each of the two cytosine molecules coordinates to the Cd ion in a bidentate chelating mode via the endocyclic N atom and the O atom. Each of the two nitrate ions also coordinates in a bidentate chelating mode, forming a bicapped distorted octahedral geometry around cadmium. The typical interligand N-H...O hydrogen bond involving two cytosine molecules is also present. In compound (III), one zinc-coordinated 5FC ligand is cocrystallized with another uncoordinated 5FC molecule. The Zn atom coordinates to the N(1) atom (systematic numbering) of 5FC, displacing the proton to the N(3) position. This N(3)-H tautomer of 5FC mimics N(3)-protonated cytosine in forming a base pair (via three hydrogen bonds) with 5FC in the lattice, generating two fused R(8) motifs. The distorted tetrahedral geometry around zinc is completed by two bromide ions and a water molecule. The coordinated and nonccordinated 5FCs are stacked over one another along the a-axis direction, forming the rungs of a ladder motif, whereas Zn-Br bonds and N-H...Br hydrogen bonds form the rails of the ladder. The coordinated water molecules bridge the two types of 5FC molecules via O-H...O hydrogen bonds. The cytosine molecules are coordinated directly to the metal ion in each of the complexes and are hydrogen bonded to the bromide, iodide or nitrate ions. In compound (III), the uncoordinated 5FC molecule pairs with the coordinated 5FC ligand through three hydrogen bonds. The crystal structures are further stabilized by N-H...O, N-H...N, O-H...O, N-H...I and N-H...Br hydrogen bonds, and stacking interactions.
合成了三种新型金属（II）-胞嘧啶（Cy）/5-氟胞嘧啶（5FC）配合物，即双（4-氨基-1,2-二氢嘧啶-2-酮-κN）二碘镉（II）或双（胞嘧啶）二碘镉（II），[CdI₂(CH₅N₃O)]，（I）；双（4-氨基-1,2-二氢嘧啶-2-酮-κN）双（硝酸根-κO,O'）镉（II）或双（胞嘧啶）双（硝酸根）镉（II），[Cd(NO₃)₂(CH₅N₃O)]，（II）；以及（6-氨基-5-氟-1,2-二氢嘧啶-2-酮-κN）水二溴化锌（II）-6-氨基-5-氟-1,2-二氢嘧啶-2-酮（1/1）或（6-氨基-5-氟胞嘧啶）水二溴化锌（II）-4-氨基-5-氟胞嘧啶（1/1），[ZnBr₂(CH₄FN₃O)(H₂O)]·CH₄FN₃O，（III），并通过单晶X射线衍射对其进行了表征。在配合物（I）中，镉离子与两个碘离子以及两个胞嘧啶分子的内环氮原子配位，形成扭曲的四面体几何构型。该结构与[CdBr₂(CH₅N₃O)] [Muthiah等人（2001年）。《晶体学报》E57，m558 - m560]同型。在化合物（II）中，两个胞嘧啶分子中的每一个都通过内环氮原子和氧原子以双齿螯合模式与镉离子配位。两个硝酸根离子中的每一个也以双齿螯合模式配位，在镉周围形成双帽扭曲八面体几何构型。还存在涉及两个胞嘧啶分子的典型配体间N - H...O氢键。在化合物（III）中，一个锌配位的5FC配体与另一个未配位的5FC分子共结晶。锌原子与5FC的N(1)原子（系统编号）配位，将质子位移到N(3)位置。5FC的这种N(3)-H互变异构体在晶格中与5FC形成碱基对（通过三个氢键），模拟N(3)-质子化胞嘧啶，产生两个稠合的R(8)基序。锌周围扭曲的四面体几何构型由两个溴离子和一个水分子完成。配位和未配位的5FC沿a轴方向相互堆叠，形成阶梯基序的梯级，而Zn - Br键和N - H...Br氢键形成阶梯的扶手。配位水分子通过O - H...O氢键桥接两种类型的5FC分子。在每个配合物中，胞嘧啶分子直接与金属离子配位，并与溴离子、碘离子或硝酸根离子形成氢键。在化合物（III）中，未配位的5FC分子通过三个氢键与配位的5FC配体配对。晶体结构通过N - H...O、N - H...N、O - H...O、N - H...I和N - H...Br氢键以及堆积相互作用进一步稳定。
