The role of reaction conditions and ligand flexibility in metal-organic hybrid materials - examples from metal diglycolates and iminodiacetates

Several new forms of transition metal diglycolates (C4H4O5) and iminodiacetates (C4H5O4N) have been synthesized hydrothermally, and their structures solved using single crystal XRD. Isostructural diglycolates of the formula M(H2O)(dga) (.) H2O (M = Co, Mn) contain 1D cavities occupied by water (Co: [1] P2(1)2(1)2(1), a = 6.8220(11) Angstrom, b = 9.9700(17) Angstrom, c = 10.9102(18) Angstrom, R-1 = 0.0206, Mn: [1] P2(1)2(1)2(1), a = 6.8796(18) Angstrom, b = 9.856(3) Angstrom, c = 11.067 Angstrom, R-1 = 0.0287). In the case the cobalt phase [1], a color change and significant structural changes accompany dehydration at 200 degreesC, yielding a new phase with reversible water absorption/desorption. A dense, anhydrous phase forms at higher temperatures, Co(dga) [2] (P2(1)2(1)2(1), a = 5.8462(12) Angstrom, b =8.1152(17) Angstrom, c = 11.223(2) Angstrom, R-1 = 0.0311). Two layered iminodiacetates are also described: Ni(H2O)(2)(ida) [3] (Pca2(1), a = 13.921(7) Angstrom, b = 5.131(3) Angstrom, c = 9.595(5) Angstrom, R-1 = 0.0315) and Co(H2O)(ida) [4] (P2(1)/c, a = 7.925(3) Angstrom, b = 10.628(4) Angstrom, e = 7.358(3) Angstrom, beta = 109.598(7)degrees, R-1 = 0.0250). These materials further illustrate both the role of higher reaction temperatures in reducing the framework water content and the importance of ligand flexibility in determining the metal-oxygen metal dimensionality in hybrid systems. (C) 2004 Elsevier Inc. All rights reserved.