Hydrothermal syntheses, crystal structures and physicochemical properties of 2-D and 3-D inorganic coordination cobalt(II)-sulfite polymers
(EN)
Chilas, G. I.
(EN)
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
(EL)
Chilas, G. I.
(EN)
The hydrothermal reaction of [Co(III)(NH(3))(6)]Cl(3) with Na(2)SO(3) yields, depending on the concentration of Na(2)SO(3), compounds {Na[Co(2)(II)(SO(3))(2)(mu(3)-OH)(H(2)O)]}(infinity) (1) and {Na(4)[Co(2)(II) (SO(3))(4)]} (2). When (NH(4))(2)SO(3)center dot H(2)O was substituted for Na(2)SO(3), the trinuclear mixed valence cobalt(II/III) complex (NH(4))(4){Co(II)[Co(III)(SO(3))(3)(NH(3))(3)](2)}center dot 2H(2)O (3 center dot 2H(2)O) was isolated. The cobalt-sulfites 1-3 center dot 2H(2)O were structurally characterized. In 1, the 1-D chains along the a-axis of the subunit [Co(I)I(2) Co(II)(3)(OH)(2)(SO(3))(2)] are cross-linked with Co(II)(1) atoms via Co-O(sulfite) and Co-O(hydroxide) bonds in 2-D sheets, that are further stacked through interlayer hydrogen bonds. In 2, the [Co(2)(II)(SO(3))(2)](infinity) chains along the b-axis are cross-linked with tetrahedral cobalts via Co(II)-O(sulfite) bonds in 2-D sheets parallel to the ab-plane and the sheets are further bound to sodium atoms via Na(+) O(sulfite) bonds to form a 3-D structure. The 3-D inorganic coordination polymer, 2, crystallizes in the non-centrosymmetric space group P2(1)2(1)2(1). In addition, in compound 2 octahedral and tetrahedral cobalt atoms coexist, which is rather unusual for cobalt clusters. Compound 3 center dot 2H(2)O is a 0-D mixed-valence {[(NH(3))(3)Co(III)(mu-SO(3))(3)]Co(II)[(mu-SO(3))(3)Co(III)(NH3) 3]} 4-trinuclear cluster and can be considered as an octahedral {Co(II)O(6)} complex ligated to two tridentate [(NH(3))(3)Co(III)(SO(3))(3)](3-) ligands. The trinuclear clusters are stacked through an extended network of hydrogen bonding into a 3-D structure. Variable temperature magnetic susceptibility studies for 1-3 center dot 2H(2)O revealed that 1 and 2 are 2-D magnetic systems with strong antiferromagnetic interaction between the Co(II) atoms leading to an S = 0 ground state for 1, while in compound 2 there is an almost zero interaction between the cobalt(II) atoms leading to a non-zero ground state. The trinuclear compound 3 center dot 2H(2)O has two diamagnetic Co(III) atoms and a high-spin Co(II) atom with D = 84(1) cm(-1), E = 6(1) cm(-1) and g = 2.56(1). The IR, the solid-state UV-vis spectra and the thermogravimetric analyses of compounds 1-3 center dot 2H(2)O are also reported.
(EN)
