Zn(II)/Cd(II) based coordination polymers synthesized from a semi-ﬂexible dicarboxylate ligand and their emission studies Mayank Gupta a , Musheer Ahmad a,b,⇑ , Ruchi Singh a , Rupali Mishra a , Jhasaketan Sahu a , Anoop K. Gupta a a Department of Chemistry, Indian Institute of Technology Kanpur, 208016, India b Department of Applied Chemistry, Aligarh Muslim University, Aligarh 202002, UP, India article info Article history: Received 17 May 2015 Accepted 14 July 2015 Available online 29 July 2015 Keywords: Coordination polymer Transition metal ions X-ray structural studies Emission studies Topology abstract Three new coordination polymers (CPs) of Zn(II)/Cd(II) have been synthesized using a dicarboxylate ligand, H 2 L = 5-(benzylamino)isophthalic acid, under hydro(solvo)thermal conditions. This ligand readily reacts with Zn(II) and Cd(II) metal salts to afford three CPs, {[Zn 8 (L) 6 (l 3 -OH) 4 (H 2 O) 6 ](DMF)(H 2 O) 2.5 } n (1), [Zn(L)] n (2) and [Cd(L)(DMF)] n (3). All the complexes have been characterized by single crystal X-ray crys- tallography (XRD), IR spectroscopy, elemental analysis, thermogravimetry (TGA) and X-ray powder diffraction (PXRD). Single crystal X-ray studies reveal that 1–3 contain homometallic clusters, with SBUs varying from dimeric to tetrameric, depending upon the metal salts as well as the reaction condi- tions. Topologically, 1 represents an sql net, whereas 2 and 3 exhibits rare ptr and fes topological nets respectively. Luminescence studies were also carried for complexes 1–3, which exhibit emissions as a pair of bands upon excitation at 405 nm. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction During the last couple of decades, a new class of organic– inorganic hybrid coordination polymers has attracted considerable attention due to their intriguing topologies and their potential application in luminescence [1–3], chemical sensors [4–6], mag- netism [7–10], gas adsorption [11–13], catalysis [14–16] and so on. Coordination networks are certainly very potential multifunc- tional luminescent materials because both the inorganic and organic moieties, separately or in conjugation, can generate emis- sions [17–20]. Metal and ligand centered charge transfers can add another dimension to the luminescent functionality within the metal organic frameworks [21–23]. The deliberate selection of organic moieties plays a pivotal role in the fabrication of CP materials with luminescence. However, more and more efforts have been focused on those organic linkers with (a) highly conjugated delocalized p electrons such as pyrene- and naphthalene chromophores (b) polycarboxylate groups such as benzene-1,4-dicarboxylate (BDC) and biphenyl-dicarboxylate (BPDC) as they impart versatile bridging modes for the formation of moderately robust CPs [24,25]. Researchers are now focusing more attention on the design of hetero-metal organic frameworks as these have revealed some unprecedented luminescent proper- ties [26]. CPs built with closed shell transition metal ions like Zn(II)/Cd(II) are good candidates in emission studies as they do not quench ﬂu- orescence intensity like those with paramagnetic metal centers [27]. Inspired from this, we have successfully synthesized a semi-ﬂexible aromatic dicarboxylate ligand, H 2 L (Scheme 1), which presumably generates luminescence due to the phenyl rings. Based on this ﬂexible dicarboxylate ligand, three coordination polymers, {[Zn 8 (L) 6 (l 3 -OH) 4 (H 2 O) 6 ](DMF)(H 2 O) 2.5 } n (1), [Zn(L)] n (2) and [Cd(L)(DMF)] n (3), have been synthesized under hydro(solvo)ther- mal conditions, which contain binuclear to tetranuclear metal clus- ters as the Secondary Building Units (SBUs). 2. Experimental 2.1. General methods and materials Reagent grade 5-aminoisophthalic acid, benzaldehyde, sodium borohydride and transition metal salts, such as Zn(OAc) 2 2H 2 O, Zn(NO 3 ) 2 6H 2 O and Cd(NO 3 ) 2 6H 2 O, were acquired from Aldrich and were used as received. All solvents, ethanol, N,N-dimethylformamide (DMF), triethylamine, acetic acid (AcOH) and NaOH, were procured from S. D. Fine Chemicals, India. All the solvents were puriﬁed prior to use following standard methods. http://dx.doi.org/10.1016/j.poly.2015.07.056 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Applied Chemistry, Aligarh Muslim University, Aligarh 202002, UP, India. E-mail address: amusheer4@gmail.com (M. Ahmad). Polyhedron 101 (2015) 86–92 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly