Zinc maleate and fumarate coordination polymers containing hydrogen-bonding capable organodiimines featuring ligand dependent in situ cis–trans isomerization Gregory A. Farnum a , David P. Martin a , Laura K. Sposato b , Ronald M. Supkowski b , Robert L. LaDuca a, * a Lyman Briggs College and Department of Chemistry, Michigan State University, East Lansing, MI 48825 USA b Department of Chemistry and Physics, King’s College, Wilkes-Barre, PA 18711, USA article info Article history: Received 27 May 2009 Received in revised form 24 July 2009 Accepted 3 August 2009 Available online 8 August 2009 Keywords: Zinc Maleate Fumarate Coordination polymer Isomerization Imine abstract Solution phase reaction at ambient temperature of zinc nitrate, maleic acid and 4,4 0 -dipyridylamine (dpa) afforded {[Zn 2 (maleate) 2 (dpa) 2 ]5H 2 O} n (1), which displayed parallel (4,4)-grid like coordination polymer layers interdigitated into double layer slab motifs via hydrogen bonding. A similar reaction employing bis(4-pyridylmethyl)piperazine (bpmp) caused in situ cis–trans isomerization of maleic acid to fumarate, and generation of [Zn(fumarate)(bpmp)(H 2 O) 2 ] n (2). Compound 2 also manifested (4,4)-grid coordination polymer layers similar to those in 1; however, the larger apertures in 2 permit 2d + 2d ? 3D mutually inclined interpenetration. Thermogravimetric and luminescence studies are also reported for 1 and 2. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction Exploratory synthesis of coordination polymer solids is a re- search focus of great current interest because of these materials’ capabilities in industrially relevant applications such as gas stor- age [1], molecular separations [2], ion exchange [3], catalysis [4], luminescence [5] and non-linear optics [6]. Among the best teth- ering ligands for divalent metal coordination polymer construc- tion are dicarboxylates, which provide the charge balance and structural scaffolding for the formation of neutral networks. The primary ligands of choice among coordination polymer research- ers have been the aromatic dicarboxylates. However, rotationally restricted a,x-dicarboxylate ligands such as the cis geometry maleate [7] and its trans congener fumarate [8] have also permit- ted the generation of coordination polymers with different topologies. The structural diversity of dicarboxylate-containing coordina- tion polymers has been enhanced by the incorporation of dipyridyl ligands, such as the chelating capping ligand 2,2 0 -bipyridine (2,2 0 - bpy) [9], its rigid-rod analog 4,4 0 -bipyridine (4,4 0 -bpy) [10], and the conformationally flexible dipodal donors 1,2-di-4-pyridyle- thane [11] and 1,3-di-4-pyridylpropane [12]. Over the past three years our group has been investigating the construction of coordi- nation polymer phases containing hydrogen-bonding capable dipyridyl ligands such as 4,4 0 -dipyridylamine (dpa) and bis(4-pyri- dylmethyl)piperazine (bpmp). These ligands’ ability to provide longer metal–metal contact distances and supramolecular points of contact have proven beneficial in the generation of aliphatic dicarboxylate coordination polymers, many displaying intriguing network topologies [13–19]. For example, {[Ni(dpa) 2 (succi- nate) 0.5 ]Cl} n displays a 5-connected self-penetrated network with a regular 6 10 topology [13], while [Ni(adipate)(dpa)(H 2 O)] n has a triply interpenetrated PtS framework (binodal 4 2 8 4 topology) [14]. {[Cd(succinate)(bpmp)(CH 3 OH)2H 2 O} n possesses a 6 5 8 lay- ered topology caused by the mismatch between the lengths of the gauche conformation dicarboxylate and bpmp ligands, avoiding for- mation of a more common (4,4) rhomboid grid [15]. {[Cu 2 (gluta- rate) 2 (bpmp)]4H 2 O} n exhibits an uncommon non-primitive cubic 6-connected self-penetrated network with 4 4 6 10 8 topology [16]. In this contribution we report the results of our synthetic explora- tions towards zinc maleate coordination polymers incorporating either dpa or bpmp. The lamellar coordination polymer {[Zn 2 (male- ate) 2 (dpa) 2 ]5H 2 O} n (1) was obtained using dpa. However, an ambi- ent temperature cis–trans isomerization of the maleic acid precursor occurred using bpmp as the co-ligand, resulting in forma- tion of the mutually inclined interpenetrated layered phase [Zn(fumarate)(bpmp)(H 2 O) 2 ] n (2). Luminescent and thermal prop- erties of these complexes are also discussed herein. 0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2009.08.005 * Corresponding author. Address: Lyman Briggs College, E-30 Holmes Hall, Michigan State University, East Lansing, MI 48825, USA. Tel.: +1 517 432 2268. E-mail addresses: laduca@msu.edu, laduca@chemistry.msu.edu (R.L. LaDuca). Inorganica Chimica Acta 363 (2010) 250–256 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica