Charge-Transfer Hybrids Containing Covalently Bonded Polyoxometalates and Ferrocenyl Units

Abstract

Two new charge-transfer hybrids with one or two ferrocenyl units covalently attached to a hexamolybdate cluster through an extended pi-conjugated bridge have been prepared using Pd-catalyzed coupling reactions on monoiodo- or diiodo-functionalized cluster substrates in over 60% yields. These hybrids have been characterized by (1)H NMR, FTIR, electrospray ionization mass spectrometry, and X-ray diffraction. The electronic spectra of these hybrids show a broad absorption tail extending beyond 550 nm, indicating the existence of charge-transfer transition from the ferrocenyl donor to the cluster acceptor. The observation of the clear charge-transfer transition indicates the contribution of charge-transfer resonance to the ground state in both 2a and 2b even though the donor-acceptor separation distance of 11.29 A is rather long, signaling a through-bond charge-transfer nature made possible by the organic pi-conjugated bridge. Cyclic voltammetry studies reveal a one-electron oxidation wave and a one-electron reduction wave for the hybrid with one ferrocenyl unit. For the one with two ferrocenyl units, a lower reduction potential and a two-electron oxidation wave are observed, indicating negligible electronic interactions between the two ferrocenyl units.

A NEW LINDQVIST-TYPE HEXAMOLYBDATE CLUSTER FUNCTIONALIZED WITH THE jt-DONOR LIGAND 4-BROMO-2,6-DIMETHYLPHENYLIMIDO: SPECTROSCOPIC, ELECTROCHEMICAL AND STRUCTURAL STUDIES

“…From the synthetic point of view, the C-Br moiety of this new precursor may be useful as an additional reaction site in this type of cluster for a further functionalization through a carbon-carbon coupling reaction, [8][9][10]13 and, potentially, with nucleophilic species to afford new molecular or polymeric hybrid materials.…”

“…2-, a number of new organoimido-derivatives of hexamolybdate, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] hexatungstate, 20 and pentatu ngstenmolybdate, 21 have been synthesized, spectroscopically characterized and, the majority, structurally authenticated by X-ray diffraction analysis. Very recently, the stability, bonding character, electronic properties, first hyperpolarizabilities of this type of complexes have also been studied by Density Functional Theory (DFT).…”

“…These observations indicate that the N-Mo π-bonding is strongly delocalized through the organic conjugated backbone. 7,13,18 The spectrum of (n-Bu 4 N) 2 [1]⋅½Me 2 CO registered in DMSO does not exhibits hipso-or bathochromic effects.…”

“…, bromo- 12,18 and iodoareneimido hexamolybdates [7][8][9][10][13][14][15] and iodoareneimido pentatungstenmolybdate 21 seems to be of great importance considering their potential applications as precursors for the synthesis of new organicinorganic hybrids containing additional organic 7,8,10,14,15 or organometallic 13 groups, or two similar clusters linked by an extended π-conjugated organic spacer. [8][9][10]15 These halogenated precursors have successfully been applied for the synthesis of organoimido-hexamolybdates as polymer pendants 5 and main-chain polymers.…”

Crystal Structure of a New POM-based Organic-Inorganic Hybrid: {[Cu(2,2'-bipy)Cl]2}n{[Na5(H2O)14](TeMo6O24)}n 2nH2O

“…1 Work on composite materials based on nanosized descrete metal-oxygen cluster anions (polyoxometalate, henceforth POM for convenience) have been qualified. 2 The great roles of POMbased organic-inorganic hybrids have been developed to apply in catalysis and medicine. 3 In this work, information about the title compound ( Fig.…”