Temperature dependent structure formation and photoluminescence studies of a series of magnesium-based coordination networks

A series of three magnesium trimesate coordination networks was synthesized from identical reaction mixtures by varying synthetic temperature. Mg(HBTC)(DMF)(2)center dot[(CH3)(2)NH] (1; BTC = trimesate; space group P6(3)/m, a = 16.596(4) angstrom, c = 14.351(8) angstrom) crystallizes at 65 degrees C, Mg-3(BTC)(HCOO)(3)(DMF)(3) (2; space group (P) over bar (3), a = 13.928(2) angstrom, c = 8.025(6) angstrom) crystallizes at 100 degrees C, and Mg-3(BTC)(2)(DMF)(4) (3; space group P2(1)/c, a = 17.490(4) angstrom, b = 11.940(2) angstrom, c = 18.460(4) angstrom, beta = 116.87(3)degrees) crystallizes at a temperature of 180 degrees C. Each network contains metal-coordinated solvent DMF molecules, but thermodynamics and solvent hydrolysis play major roles in structure formation. Compounds 1 and 2 are two-dimensional networks which incorporate hydrolysis byproducts. Compound 3 is a three-dimensional network and shows no inclusion of byproducts. The series follows the trend of increased network connectivity resulting from increased temperature. Each of the networks show a weak photoluminescence response, suggesting that coordinated solvent molecules and interlayer species play a role in quenching photoluminescence. (C) 2012 Elsevier B.V. All rights reserved.