Honeycomb nets with interpenetrating frameworks involving iminodiacetato-copper(II) blocks'and bipyridine spacers: Syntheses, characterization, and magnetic studies

Three coordination polymers of copper(II), viz. {[Cu(ida)(4,4'-bipyH)]ClO4}(infinity) (1), {[Cu-2(ida)(2)(mu-4,4'-bipy)].2H(2)O}(infinity) (2), and [Cu-2(ida)(2)(bpa)](infinity) (3) have been synthesized by the process of self-assembly using Cu(ida) [ida = iminodiacetate(2-)] as the building block and 4,4'-bipyridyl and 1,2-bis(4-pyridyl)ethane (bpa) as linkers. Crystals of 1 are orthorhombic, of space group Pna2(1), with a = 13.8956(12) Angstrom, b = 16.3362(16) Angstrom, c = 7.3340(12), and Z = 4. Both compounds 2 and 3 crystallize in monoclinic space group P2(1)/a with a = 10.1887(8) Angstrom (9.6779(10) Angstrom for 3), b = 8.0008(11) Angstrom (9.1718(10) Angstrom), c = 11.6684(9) Angstrom (12.9144(12) Angstrom), beta = 98.307(11)degrees (102,796(18)degrees), and Z = 2 (2). Compound 1 has a zigzag chain structure with an extensive hydrogen-bonded network while compounds 2 and 3 are honeycomb (6,3) nets with interpenetrating structures. Variable temperature (2-300 K) magnetic study indicates the presence of weak antiferromagnetic interactions (J = 0.82 +/- 0.01 cm(-1)) in 1 and ferromagnetic in 2 (J = -0.45 +/- 0.05 cm(-1)) and 3 (J = -0.21 +/- 0.02 cm(-1)). The extent of planarity of the bridging "Cu-O-C-O-Cu" moiety, acting as the super-exchange pathway between the neighboring copper centers, probably controls the sign of the magnetic exchange coupling in these compounds.