Dynamics of bound states of dihydrogen at Cu(I) and Cu(II) species coordinated near one and two zeolite framework aluminium atoms: A combined sorption, INS, IR and DFT study

Abstract Ambient conditions sorption isotherms of dihydrogen in a series of various levels of Cu-exchanged ZSM-5 zeolites, with two different Si/Al ratios, namely 11.5 and 25, show the presence of different amount of Cu centres able to strongly bind H2. Although the isosteric heats of adsorption derived from these isotherms are rather similar, of the order of 30 kJ/mol H2, Inelastic Neutron Scattering (INS) of adsorbed dihydrogen and Fourier-Transformed Infra-Red (FTIR) spectroscopy measurements of adsorbed CO and NO reveal that copper is encountered in two oxidation states. At least two types of Cu(I) ions are clearly detected as well as some heterogeneity of the Cu(II) species. The number of these Cu species is different in the two investigated ZSM-5 materials and depends on the Cu exchange level. With the aid of DFT model cluster calculations we find that under different coordination environments, determined by the Al distribution, both mono- and divalent Cu ions could bind H2 with a different strength. Unprecedentedly, we found that Cu-ions compensating two Al atoms, i.e. formally Cu(II) species, relatively far apart from each other, may behave very similarly to the monovalent Cu-species or alternatively viewed – as Cu(I) species that compensate for two framework Al-atoms. Such Cu-species also form stable η2 dihydrogen complexes

An introduction to the special issue on interplay of crystallography, spectroscopy and theoretical methods for solving chemical problems

Special issue on Interplay of crystallography, spectroscopy and theoretical methods for solving chemical problems.-- Editorial.Peer Reviewe

Assembling Metal Clusters with Covalent Linkers. Synthesis and Structure of a Roughly Planar Pt18 Derivative Containing Five Clusters Connected by sigma-Alkynyl Spacers

Sterically protected tri- and hexanuclear platinum clusters were used as building blocks for the high-yield synthesis of a first-generation dendrimer (see picture; tBu groups are omitted for clarity), which is chemically and thermally stable, and in which the cluster units are separated by conjugated 1,3,5-triethynylphenyl groups

Steric and polar effects in free-radical reactions. - An unusual type of azocoupling by free radical decomposition of diazonium salts

A new free-radical azocoupling has been accomplished by decomposition of diazonium salts with monoelectronic reducing agents in the presence of 4-methyl-3-penten-2-one. Steric and polar factors are responsible of the unusual behaviour. © 1980