Cite this: CrystEngComm, 2013, 15, 2099 The influence of water molecule coordination onto the water–aromatic interaction. Strong interactions of water coordinating to a metal ion3 Received 22nd April 2012, Accepted 18th December 2012 DOI: 10.1039/c2ce25621e www.rsc.org/crystengcomm Dubravka Z. Vojislavljevic ´, a Goran V. Janjic ´, b Dragan B. Ninkovic ´, a Agnes ˇ Kapor c and Snez ˇana D. Zaric ´* de The interactions between water molecules (non-coordinating and coordinating) and aromatic rings were studied by analyzing data in the Cambridge Structural Database and by quantum chemical calculations. The results show the influence of water coordination to a metal ion; interactions of coordinating water are stronger. The MP2/def2-QZVP interaction energies of non-coordinating water and neutral aqua complexes [ScCl 3 (H 2 O) 3 ], [ZnCl 2 (H 2 O) 4 ], [CdCl 2 (H 2 O) 4 ], and [ZnCl 2 (H 2 O) 2 ] with benzene molecule are 23.36, 25.10, 25.43, 26.86, and 25.14 kcal mol 21 , respectively. Interactions of charged aqua complexes [ZnCl(H 2 O) 5 ] + and [Zn(H 2 O) 6 ] 2+ are stronger, 29.69 and 213.96 kcal mol 21 , respectively. The calculations also reveal strong long-range interactions: at the distance of 3.0 Å the interaction energies of neutral complexes are in the range of 24.11 to 24.91 kcal mol 21 , while interaction energies of charged complexes are 26.37 and 210.76 kcal mol 21 . Introduction The interaction of water molecule with aromatic systems is of large importance in many systems from biological molecules to materials. 1–5 The experimental results showed important interactions of aromatic rings with water molecules in aquaporins (water-transporting proteins), 3 nanotubes, 4 and nanoporous materials. 5 The water–benzene complex has been the subject of extensive investigation. 6 Most theoretical studies agree that the minimum energy structure of the water–benzene dimer is the structure with OH–p interaction, with the water above the ring oriented to form a single hydrogen bond with the ring. Recently, OH–p interaction between liquid water and benzene was experimentally observed. 7 The results imply that OH–p interaction occur at hydrated biological interfaces and play an important role in biological binding, recognition, and signal- ing processes. Interactions of a water molecule with ions, molecules, and interfaces have been intensively studied. 8,9 It is well-known that properties of water are substantially influenced by the presence of ions. 10 Here, we studied the influence of a metal ion on water– aromatic interactions. Based on analysis of crystal structures from the Cambridge Structural Database (CSD) and high level ab initio calculations we studied the interactions of non- coordinating and of coordinating water molecules. The results showed larger interaction energies of coordinating water. To the best of our knowledge this is the first study describing influence of water coordination on water–aromatic interac- tions and calculated interaction energies of coordinating water. Methods Searching the Cambridge Structural Database The CSD (version 5.31, updated May 2010 11 ) was searched for the intermolecular OH–p interactions of non-coordinating and of coordinating water molecules with C 6 -aromatic groups. Structures satisfying the following criteria were extracted: (a) the crystallographic R factor less than 10%; (b) error-free coordinates according to the criteria used in the CSD system; (c) no crystallographic disorder; (d) no polymeric structures; (e) positions of all hydrogen atoms normalized using the ConQuest program (version 1.13). 12 The structure was con- sidered as a hit if the distance between a hydrogen atom of the a Innovation Center, Department of Chemistry, University of Belgrade, Studentski trg 12–16, 11000 Belgrade, Serbia b ICTM, University of Belgrade, Njegos ˇeva 12, 11000 Belgrade, Serbia c Department of Physics, Faculty of Sciences, University of Novi Sad, Trg D.Oradovic ´a 4, 21000 Novi Sad, Serbia d Department of Chemistry, University of Belgrade, Studentski trg 12–16, 11000 Belgrade, Serbia. E-mail: szaric@chem.bg.ac.rs e Department of Chemistry, Texas A & M University at Qatar, P. O. Box 23874 Doha, Qatar 3 Electronic supplementary information (ESI) available. See DOI: 10.1039/ c2ce25621e CrystEngComm PAPER This journal is ß The Royal Society of Chemistry 2013 CrystEngComm, 2013, 15, 2099–2105 | 2099 Downloaded by University Novi Sad on 09/04/2013 12:11:32. Published on 18 December 2012 on http://pubs.rsc.org | doi:10.1039/C2CE25621E View Article Online View Journal | View Issue