ABSTRACT
A novel cadmium complexes of {[Cd(H2 biim)2 (SO4)] x 3H2O}n(1) (H2 biim = 2,2'-biimidazole) was synthesized by hydrothermal reaction of 3CdSO4 x 8H2O and 2,2'-biimidazole ligand. The complex was built up by [Cd(H2 biim)2]2+ units bridged sequentially by SO4(2-) anions to form 1D zigzag chains parallel to the c-axis. The H2biim ligands were attached to the 1D chain as branches of the chain by coordinating to Cd2+ at two sides of the chain. The chains were held together by pi--pi interaction and O--H***O interactions, thus yielding a 3D extended supramolecular network The responses of symmetric stretching vibration of SO4(2-), N--C single bond, N==C double bond and anti-symmetric stretching vibration of N-C single bond were detected in 2D IR correlation spectra under thermal perturbation. The complex exhibited strong blue emission peak at 498 nm (lambda(ex) x = 397 nm) that can be assigned to a ligand-to-metal charge-transfer (LMCT) band.
ABSTRACT
Three α-Keggin heteropolymolybdates with the formula [(C(5)H(4)NH)COOH](3)[PMo(12)O(40)] 1, {[Sm(H(2)O)(4)(pdc)](3)}{[Sm(H(2)O)(3)(pdc)]}[SiMo(12)O(40)]·3H(2)O 2 and {[La(H(2)O)(4)(pdc)](4)}[PMo(12)O(40)]F 3 (H(2)pdc = pyridine-2,6-dicarboxylate), have been synthesized under hydrothermal condition and characterized by single crystal X-ray diffraction analyses, elemental analyses, inductively coupled plasma atomic emission spectroscopy (ICP-AES), IR, thermal gravimetric analyses, thermal infrared spectrum analyses and powder X-ray diffraction (PXRD) analyses. Single crystal X-ray diffraction indicates all three compounds comprise ball-shaped Keggin type [XMo(12)O(40)](n-) polyoxometalates (POMs) (n = 3, X = P; n = 4, X = Si, respectively) with different types of carboxylic ligands derived from H(2)pdc, and these cluster anions are isostructural. In order to explore structural characteristics, Rhodamine B photocatalytic (RhB) degradation and two-dimensional infrared correlation spectroscopy (2D-IR COS) tests, are investigated for 1, 2 and 3. In RhB degradation, all compounds show good photocatalytic activity. For 1, the activity mainly comes from POMs. While in 2 and 3, POMs' photocatalytic activity is enhanced by the Ln(iii)-pdc metal-organic frameworks. Structural properties like POM's stability and magnetic sensitivity are discussed by 2D-IR COS under thermal/magnetic perturbations.
ABSTRACT
A novel polyoxovanadium borate Mn2[V12B16O52 (OH)6](en)2 (H3O)6 (H2O)5 1(en = ethylenediamine) was hydrothermally synthesized and characterized by IR, two-dimensional infrared (2D IR) correlation spectroscopy with magnetic and thermal perturbation, and single crystal X-ray diffraction. In 1, it is interesting that each [V12B16O52 (OH)6]14- units is connected by four [Mn(H2O)2]2+ to generate a 2D layer on the ab plane. Along c axis, these layers are further linked by H-bond to form a 3D framework. The response of the stretching vibrations of B-O, V-O-V and Mn-O-B was detected in the 2D IR correlation spectra with magnetic perturbation. In addition, the response of the stretching vibrations of B-OH, B-O, V-O-V and Mn-O-B was detected in the 2D IR correlation spectra with thermal perturbation.
