CrystEngComm PAPER Cite this: CrystEngComm, 2014, 16, 654 Received 3rd September 2013, Accepted 5th October 2013 DOI: 10.1039/c3ce41765d www.rsc.org/crystengcomm An unusual nitroso⋯nitroso interaction in the coordination polymer structures of Ni(II) and Co(II) complexes with the α,ω-bis(benzotriazoloxy)alkane system† Sandeepta Saha, a Ashok Sasmal, a Guillaume Pilet, b Antonio Bauzá, c Antonio Frontera c and Samiran Mitra * a A novel type of NO⋯NO supramolecular interaction is reported for the first time. Three new polymeric coordination complexes, two nickel(II) complexes, {[Ni(μ-L 1 ) 2 (NCS) 2 ]} n ,(1) {[Ni(μ-L 2 ) 2 (NCS) 2 ]} n ,(2) and a cobalt(II) complex {[Co(μ-L 3 ) 2 (NCS) 2 ]} n (3) have been synthesized with the organic ligand α,ω- bis(benzotriazoloxy)alkane (L 1 = 1,3-bis(benzotriazol-1-yl)-1,3-dioxapropane; L 2 = 1,5-bis (benzotriazol-1- yl)-1,5-dioxapentane; L 3 = 1,6-bis(benzotriazol-1-yl)-1,6-dioxahexane) and thiocyanate as counterions. The complexes were characterized by various physical measurements such as elemental analysis, FT-IR, UV–Vis, NMR and mass spectroscopy. The single crystal X-ray analysis revealed that complexes 1 and 2 have a 1D coordination polymer helical structure whereas complex 3 has a 2D polymer anti corrugate structure. Complexes 2 and 3 were found to be involved in packing in the crystal structures by a very unusual anti-parallel strong NO⋯NO interaction. In addition, the π-acidity of the triazole ring moiety increased upon the coordination of the Ni ion which led to the establishment of lone pair–π (lp–π) inter- actions. Moreover, all of the complexes show different intermolecular interactions (H-bonds, π–π, lone pair–π and anti-parallel NO⋯NO) whose energetics and role in the crystal packing have been evaluated with theoretical DFT calculations. Introduction The discovery of the involvement of nitric oxide (NO) in sev- eral physiological and pathophysiological processes launched a spectacular increase in studies in areas such as chemistry, biochemistry and pharmacology. The noncovalent interac- tions that govern molecular recognition processes ranging from crystal growth to the formation of protein–ligand and protein–protein complexes, apolar (hydrophobic) interac- tions, ion–ion, ion–dipole interactions, and hydrogen- bonding association have been the preferred subjects for a large number of investigations during the past few decades. 1 A wealth of information on the nature and energetics of these interactions has greatly enhanced our ability to use them for crystal structure prediction, 2 crystal engineering, 3 supramo- lecular synthesis 4 and structure based ligand design. 5 How- ever, much less attention has been given to the role that multipolar interactions play in molecular recognition events. Although a number of crystal structure analyses and database searches by Gavezzotti, 6 Allen et al., 7 Lee et al., 8 and others have highlighted the main types of interaction geometries for participating dipoles, particularly the head-to-tail and anti- parallel orientations. Much of this interest has focused on the interactions between the dipolar carbonyl groups, due to their high incidence and structural importance across the broad spectrum of compounds. Nevertheless, chemical bonds and the –CN group exhibit local dipole moments which are similar to that of the carbonyl group, and these interactions have implications in crystal engineering which have been explored. 9 But, intermolecular NO⋯NO dipolar interactions have not been reported till date. Here we explore the experi- mental evidence for the NO⋯NO interactions. Moreover, the design and construction of metal–organic frameworks (MOFs) have attracted a considerable interest to a Department of Chemistry, Jadavpur University, Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India. E-mail: samiranju92@gmail.com; Fax: +91 33 2414 6414; Tel: +91 33 2414 6666 (extn. 2779) b Groupe de Crystallographie et Ingénierie Moléculaire, Laboratoire des Multimatériaux et Interfaces, UMR 5615 CNRS-Université Claude Bernard Lyon 1, Bât. Chevreul, 43 bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France c Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, Baleares, 07122 Palma de Mallorca, Spain † Electronic supplementary information (ESI) available. CCDC numbers 945176, 882003 and 882002 contain the supplementary crystallographic data for 1, 2 and 3 respectively. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3ce41765d 654 | CrystEngComm, 2014, 16, 654–666 This journal is © The Royal Society of Chemistry 2014 Published on 08 October 2013. Downloaded by Jadavpur University on 15/05/2014 18:30:33. View Article Online View Journal | View Issue