摘要:

A series of luminescent tetranuclear copper(I) and silver(I) chalcogenide complexes have been synthesized and characterized. The photophysical and photochemical properties of these complexes have also been investigated. The long-lived excited state of these luminescent clusters is believed to bear a high parentage of ligand-to-metal charge-transfer LMCT (E2-→ M4) character. The assignment has also been supported by molecular orbital calculations.

ISSN:0260-3594    

DOI:10.1080/02603599708032737

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Solubilities of some divalent lanthanide and actinide sulfates were evaluated and compared with the solubilities of alkaline earth sulfates. It has been concluded that the shift of the solubilities of LnSO4and AnSO4towards the solubility of BaSO4is a consequence of differences in the aquo ion structure between [Ln(OH2)9]aq2+, [An(OH2)9]aq2+, [Ba(OH2)9]aq2+and [Ra(OH2)9]aq2+vs. [Sr(OH2)8]aq2+and [Ca(OH2)8]aq2+. This difference in the primary hydration number throws light on the problem of the nomadic behavior of Eu(II) which, depending on the system, migrates from Ca(II) to Ba(II) on plots of the Gibbs solution and complexation energies. The virtual absence of the covalent shortening in the Euaq2+aquo ion slightly enlarges the Eu2+ion, and this makes its primary hydration number higher by 1 than that of the Sr2+ion. The increase in the coordination number (CN) for the Euaq2+species with respect to the Sraq2+species is supported by the solution enthalpy and entropy values of the respective sulfates. In particular, the difference in the primary hydration explains why the solubility product of EuSO4is about two orders of magnitude lower than that of SrSO4and close to BaSO4, while the stability of the Eu(II) complexes with EDTA, DCTA and 2-picolinic acid is close to that for the respective Ca complexes. The stronger interactions in the octaaquaions(II) than in the nonaaquaions(II) is the reason why, in oposition to Sr2+, the ions of Eu2+, Yb2+and Es2+form inner sphere complexes with tetraphenylborate anions in aqueous-ethanolic solutions. The same reason elucidates why, contrary to the Lnaq2+and Anaq2+species, Sraq2+does not form complexes with o-phenantroline and dipirydyl.

ISSN:0260-3594    

DOI:10.1080/02603599708032738

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper is focused on some aspects of the sol-gel process as a solution chemistry route to the preparation of materials. This field is opening new possibilities for molecular chemistry in the synthesis of metastable solids. Three ways emphasizing these possibilities are presented here: (1) the use of precursors containing functional groups for the preparation of solids with specific chemical reactivity leading to metastable phases; (2) the nonhydrolytic sol-gel process for the synthesis of monocomponent oxides with various structures, and of homogeneous bicomponent oxides; (3) organic—inorganic hybrid solids containing covalent bonds. The chemical reactivity of these solids is used as evidence for the presence of substructures which depend on the geometry of the organic moiety.

ISSN:0260-3594    

DOI:10.1080/02603599708032739

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0260-3594    

DOI:10.1080/02603599708032736

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor