Inorganic Chemistry, Vol.53, No.3, 1320-1330, 2014
Formation of Coordination Polymers or Discrete Adducts via Reactions of Gadolinium(III)-Copper(II) 15-Metallacrown-5 Complexes with Polycarboxylates: Synthesis, Structures and Magnetic Properties
Reactions of the copper(II)-gadolinium(III) 15-metallacrown-5 complex [GdCu5(Glyha)(5)(NO3)(2)(H2O)(6)](NO3) (Glyha(2-) = dianion of glycinehydroxamic acid) with different di/tricarboxylates (1,3-phthalate, 1,4-phthalate, biphenyl-4,4'-dicarboxylate, citrate) resulted in formation of different types of products: {[(GdCu5(Glyha)(5)(H2O)(2))(GdCu5 (Glyha)(5) (H2O)(3)) (1,3 - bdc) 3]center dot 16H(2)O}(n) (1), {[(GdCu5(Glyha)(5)(H2O)(3))(2)(1,4-bdC)(2)](1,4-bdC)center dot 8H(2)O}(n) (2), {[(GdCu5(Glyha)(5)(H2O)(4))(2)(1,4-bdc)(3)]center dot 8H(2)O}(n) (3), [GdCu5(Glyha)(5)(Citr)-(H2O)(4)]center dot 7H(2)O (4), {[GdCu5(Glyha)(5)(H2O)(5)](mu(2)-CO3)[Cu(Fgg)]}center dot 7H(2)O (5) and [Cu(Gly)(2)(H2O)] (6) (where bdc(2-) is the corresponding phthalate (benzenedicarboxylate), Citr(3-) is citrate, Fgg(3-) is the trianion of [(Nformylaminoacetyl)amino]acetic acid and Gly(-) is glycinate). Complexes 1-5 contain the [GdCu5(Glyha)(5)](3+) cation. Complexes 2 and 3 possess the same composition but differ by the mode of p-phthalate coordination to the [GdCu5(Glyha)(5)](3+) unit. In compounds 1-3, metallacrown cations are linked by the corresponding phthalates in ID, ID and 2D polymers, respectively, whereas 4 and 5 are discrete molecules. Compound 5 is the product of a multistep reaction, which finally involves atmospheric CO2 capture. Hydrolysis of hydroxamate in this reaction is confirmed by isolation of a mononuclear copper glycine complex 6. The chi T-M vs T data for 1 were fitted using a model based on the Hamiltonian (H) over cap (GdCu5) = -2J(1)(S-1 x S-Gd + S-2 x S-Gd + S-3 x S-Gd + S-4 x S-Gd + S-5 x S-Gd) -2J(2)(S-1 x S-2 + S-2 x S-3 + S-3 x S-4 + S-4 x S-1 + S-5 x S-1. The best fit corresponded to J(1) = +0.60(2) cm(-1), J(2) = -61.0(5) cm(-1) and zJ' = -0.035(4) cm(-1). Complex 1 is the first example of a 15-metallacrown-5 system, for which numerical values of exchange parameters have been reported. The isotherm for methanol absorption by compound 1 at 293 K was typical for microporous sorbents, whereas ethanol sorption was negligibly small.