Coordination polymers and hydrogen-bonded assemblies of 2,2′-[2,5-bis-(carboxymethoxy)-1,4-phenylene]-diacetic acid with ammonium, lanthanum and zinc cations

Hatem M. Titi, Anirban Karmakar, Israel Goldberg

Research output: Contribution to journalReview articlepeer-review

Abstract

We report the synthesis of the 2,2′-[2,5-bis-(carboxymethoxy)-1,4- phenylene]diacetic acid (TALH4) ligand and the structures of its adducts with ammonium, namely diammonium 2,2′-[2,5-bis-(carboxymethyl)-1, 4-phenylenedi-oxy]diacetate, 2NH4+·-C 14H12O102-, (I), lanthanum, namely poly[[aquabis-[μ4-2,2′-(2-carboxylatomethyl-5-carboxymethyl- 1,4-phenylenedioxy)diacetato]dilanthanum(III)] monohydrate], {[La 2(C14H11O10)2(H 2O)]·H2O}n, (II), and zinc cations, namely poly[[{μ4-2,2′-[2,5-bis-(carboxymethyl)-1,4- phenylenedi-oxy]diacetato}-zinc(II)] trihydrate], {[Zn(C14H 12O10)]·3H2O}n , (III), and poly[[diaqua(μ2-4,4′-bipyrid-yl){μ4-2, 2′-[2,5-bis-(carboxymethyl)-1,4-phenylenedioxy]diacetato}dizinc(II)] dihydrate], {[Zn2(C14H10O10)(C 10H8N2)(H2O)2]·2H 2O}n , (IV), the formation of all four being associated with deprotonation of TALH4. Adduct (I) is a diammonium salt of TALH22-, with the ions located on centres of crystallographic inversion. Its crystal structure reveals a three-dimensional hydrogen-bonded assembly of the component species. Reaction of TALH4 with lanthanum trinitrate hexa-hydrate yielded a two-dimensional double-layer coordination polymer, (II), in which the LaIII cations are nine-coordinate. With zinc dinitrate hexa-hydrate, TALH4 forms 1:1 two-dimensional coordination polymers, in which every ZnII cation is linked to four neighbouring TALH22- anions and each unit of the organic ligand is coordinated to four different tetra-hedral Zn II cation connectors. The crystal structure of this compound accommodates molecules of disordered water at the inter-face between adjacent polymeric layers to give (III), and it has been determined with low precision. Another polymer assembly, (IV), was obtained when zinc dinitrate hexa-hydrate was reacted with TALH4 in the presence of an additional 4,4′-bipyridyl ligand. In the crystal structure of (IV), the bipyridyl and TAL4- entities are located on two different inversion centres. The ternary coordination polymers form layered arrays with corrugated surfaces, with the ZnII cation connectors revealing a tetra-hedral coordination environment. The two-dimensional polymers in (II)-(IV) are inter-connected with each other by hydrogen bonds involving the metal-coordinated and noncoordinated molecules of water. TALH4 is doubly deprotonated, TALH 22-, in (I) and (III), triply deprotonated, viz. TALH 3-, in (II), and quadruply deprotonated, viz. TAL4-, in (IV). This report provides the first structural characterization of TALH 4 (in deprotonated form) and its various supra-molecular adducts. It also confirms the potential utility of this tetra-acid ligand in the formulation of coordination polymers with metal cations.

Original languageEnglish
Pages (from-to)m238-m244
JournalActa Crystallographica Section C: Crystal Structure Communications
Volume66
Issue number9
DOIs
StatePublished - Sep 2010

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