Formation of infinite 2D water layers in a crystal host

Available online at www.sciencedirect.comCHINESEScienceDirectC HEMICALL .ETTERSELSEVIERChinese Chemical Letters 20 (2009) 861- 864www.elsevier.com/locate/ccletFormation of infinite 2D water layers in a crystal hostCai Hua Zhou**, Li Jun Zhou°, Long Tang", Yao Yu Wang“Department of Chemistry & Chemical Engineering, Yan' an University, Yan'an 716000, PR Chinab Department of Chemistry/Shaanxi Key Laboratory of Physico inorganic Chemistry, Northwest University, Xi an 710069, PR China° Department of Applied Chemistry, Xidian Universit, Xi an 710071, PR ChinaReceived 22 September 2008AbstractA self assembled, (H2O)38 cluster stabilized by a mono nuclear copper(I) complex 1 namely {[Cu(phen)2(CO3)]-7H2O} ischaracterized by X-ray diffraction studies. The adjacent (H2O)38 clusters connect together resulting in an infinite 2D water layerstructure. The water morphology is stable at room temperature, but upon thermal decomposition, the water loss is irreversible.◎2009 Cai Hua Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.Keywords: Water cluster, Supramolcular; Hydrogen. bondingBeing water plays an indispensable role in life-sustaining processes, investigations on the structure, properties andfunctions of water have received more attention than any other substance [1-3]. Structural studies on“discrete'”waterclusters within the lattice of a crystal host have significantly advanced our knowledge toward the first step ofunderstanding the behavior of bulk water [4 -6]. Growth of larger water clusters, and how these clusters linkthemselves to form a larger network of water molecules is still a challenging scientific endeavor [7- -9]. A surge ofpublications dealing with the structure of some interesting polymeric water molecule motifs in crystal hydrates oforganic compounds and coordination complexes has appeared [10- 14]. Very recently, two-dimensional (2D) waterl/icelayers containing large 10-, 12-, 18- and 45-membered water rings have been observed in the solid state [15-19]. Thesepolymeric water morphologies, the size of which lies in between water clusters and bulk water, have physicalproperties very closely associated with those of bulk water. Therefore, the above studies have significantly advancedthe understanding of water structures as well as provided novel structural aspects of water and new insights into waterwith implications for biological environments. Herein, we describe the formation of an unprecedented, infinite 2Dwater layer consisting of (H2O)38 clusters stabilized by a crystal host (complex 1), where each cyclic (H2O)38 clusterconsists of six five-membered rings and two four-membered rings. Hydrogen-bonding interactions between the 2Dlayers of water and complex 1 create a unique, infinite through-channel.Single-crystal diffraction analysis [20] reveals that 1 contains two phenanthroline ligands, one Cu(II), onecarbonate dianion, and seven free water molecules in the asymmetric unit. Four pyridine nitrogen atoms from twophenanthroline ligand units and two oxygen atoms from carbonate dianion coordinated Cu(I)， leading to anoctahedral geometry structure. There lies a bidentate binding mode of the carbonate ligand, the extension of these Cu-Corresponding author.E-mail adress: xbdxzch@ 126. com (C.H. Zhou).中国煤化工1001-8417/$ - see front matter◎2009 Cai Hua Zhou. Published by EIlsevier B.V. on IMYHCNMHGAll rights reserved.doi: 10.1016/.cclet.2009.03.030862C.H. Zhou et al./ Chinese Chemical Letters 20 (2009) 861- -864。01。「0294Fig. 1. 2D sheet structure in crystalographic ab plane (hydrogen atoms are onitted for clarity).O bonds [Cu- _O5 2.287(6) and Cu- _O4 2.683 (6) A] should ascribe to the Jahn- -Teller effect. The complex 1 isassociated with free water molecules through O1-H.. .O9w, O2- -H..O4w，03- H..O4w and O3- H.. .O6w .hydrogen-bonding interactions form a 2D sheet structure in crystallographic [0 01] plane (Fig. 1). The 2D sheets arefurther extended along [0 01] plane by hydrogen bonds among water molcules generating a 3D supramolecularstructure. (see supporting information, Fig. S2).n order to investigate the function of organic-metal complexes stabilizing various water topologies irenvironments resembling those in living systems, we have examined the topology structure of the supramolecularassembly of the water molecules. Seven water molecules exist in coordination complex crystal host, which formed aninfinite 2D water layer in the [1 0 0] plane by hydrogen bonds. The 2D water layer is composed of a unique (H2O)38cluster with symmetric center (Fig.2), which is formed by a type of tetramer and a type of pentamer. Basically, the905010ρ9.....中国煤化工MYHCNMHGFig. 2. The 2D layer of water is composed of a unique (H2O)38 clusters (hydrogen atoms are omitted for clarity).C.H. Zhou et al./Chinese Chemical Letters 20 (2009) 861- 864863(H2O)38 cluster unit is an assembly of six (H2O)s and two (H2O)4 subunits. Water molcules connected together byhydrogen bonds. According to the classification system of common aggregation states adopted by hydrogen-bondedwater molecules [21], this cycle (H2O)38 belongs to a L38(10)5(2)4(2)4(1) pattern, and it possesses D2a-symmetry.Although the data collction for the complex 1 is carried out under liquid-nitrogen temperature conditions (100 K)most of the water hydrogen atoms were never located, however, positions of the water molecules constituting the 2Dsupramolecular architecture were determined unequivocally. The subunit (H2O)s comprised five different oxygenatoms (O6w, O7w, O8w, O9w, O10w) whose conformation is similar to cyclopentane with one water molecule raisingup above the plane formed by the other four oxygen atoms. The water pentamer topology described here is inagreement with the puckered ring achieved from both experimental and theoretical studies by Liu et al. [22]. Adjacentpentamers connected each other by the way of centers of inversion, these pentamers produce a 1D T4(2)5(2) water tapealong c axis via hydrogen bonds between O7w and O9w, O8w and O10w (see supporting information, Fig. S2).Another (H2O)4 subunit is formed by two symmetry-related O4w and O5w presenting a rigid parallelogram geometry,and the distances of the length and width, that is, the two distinct O4w. . .O5w distances are 2.843 and 2.939 A,respectively. The hydrogen bonds (O5w. . .O6w) link this parallelogram geometry (H2O)4 with the neighboring(H2O)s subunit along the b axis, and finally result in the formation of a big (H2O)38 cluster. However, we consider“bridged tetramers" are a more appropriate description for the (H2O)4 subunit, because the bond distance ofO5w.. .O6w is 2.930 A, which is longer than O- 0 average bond distance (2.8398 A) in (H2O)38 cluster. Formation ofthe 2D water layered is generated by simple shift of the (H2O)38 cluster, when viewed down the a axis. Alternatearrangement of the complex 1 and the 2D-layered water produce infinite through-channels along a direction. The CPKdiagram of the 3D supramolecules structure clearly shows that the phenyl rings of the coordination complex 1 arelocated inside these channels.Interestingly, the hydrogen-bonding motif of the 2D water layer of (H2O)38 clusters in the self-assembled systempresented herein, in which three water molecules (O6w, O4w, O9w) are involved in the formation of four hydrogenbonds, and others (O5w, O7w, O8w, O10w) are involved in the formation of three hydrogen bonds. Apart from theinteractions with the surrounding cyclic water rings, the O4w water molecule of the tetramer has hydrogen-bondinginteraction with two oxygen atoms (O2, O3) of carbonate dianion in the complex 1. Whereas O6w and O9w watermolecule of pentamer are also forming O. . .0 short contacts with the O3 and O1 of carbonate dianion, respectively, theranges of hydrogen bonds between waters and carbonate dianion are from 2.634 to 2.698 A. The geometry of the 38-membered basic ring is imposed by the cooperative effect which include Ow. . .Ow interactions between fused four-and five-membered rings and 0- H. . .Ow interactions among water molecules and complex 1.In summary, we have characterized a novel 2D water layer structure composed by a unique (H2O)38 cluster. Thisnew (H2O)38 cluster has D2a symmetry structure. The manner of self- assembled tetrameric water and pentamericclusters during the formation of (H2O)38 cluster is unprecedented. We believe that the water structure demonstratedherein brings to a novel mode of the cooperation for water molecules self-assemble. This discovery is helpful inimproving the modeling of some of the unexplained properties of water.AcknowledgmentsThis work is supported by the Natural Science Foundation of Shaanxi Province (No. 07JK439).Appendix A. Supplementary dataSupplementary data associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2009.03.030.Reference[] P. Ball, H2O: A Biography of Water, Weidenfeld & Nicolson, London, 99.[2] R. Ludwig, Angew. Chem. Int. Ed. 40 (2001) 1808.[3] K. Nauta, R.E. Miller, Science 287 (2000) 293.中国煤化工[4] F.N. Keutsch, J.D. Cruzan, R.J. Saykally, Chem. Rev. 103 (2003) 2533.MHCNMH G .[5] LJ. Barbour, G.W. Orr, J.L. Atwood, Nature 393 (1998) 671.[6] J.L. Atwood, LJ. Barbour, TJ. Ness, PL. Raston, J. Am. Chem. Soc. 123 (2001) 7192.864C.H. Zhou et al./Chinese Chemical Letters 20 (2009) 861- -864[7] A. Miller, E. Krickemeyer, H. Bogge, M. Schmidtmann, B. Botar, M.O. Talismanova, Angew. Chem. Int. Ed. 42 (2003) 2085.[8] R.J. Doedens, E. Yohannes, MI. 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