Volume 228, Issue 4 -

A new strontium-containing layered silicate, a lkaline e arth-containing s ilicate (AES)-18 [chemical composition: Si 16 O 24 (OH) 16 · {Sr(OH) 2 } 8 · (KOH) 2 ], was synthesized utilizing a mechanochemical reaction in which an admixture of strontium hydroxide, which unfavorably precipitates in conventional syntheses, and a fumed silica (Aerosil) was allowed to react in the solid phase. The crystal structure of AES-18 was elucidated by the charge-flipping method using powder X-ray diffraction data, and the obtained structure was refined by a combination with the Rietveld method and the maximum entropy method (MEM). The structure analyses showed a tetragonal symmetry with a = 0.912738(3) nm, c = 1.628120(8) nm, and the space group P 4 2 / mnc . Two silicate layers composed of Q 3 local structure [(—SiO) 3 Si—OH], 7-coordinated Sr 2+ catäions, and K + cations were included in a unit cell, and a Sr 4 (OH) 17 cluster was formed between adjacent silicate layers. The framework topology of AES-18 containing 4- and 8-Si-membered rings was similar to that of paracelsian.

The location of physisorbed CO 2 molecules on silicalite-1 zeolite (MFI-type) is determined using a single-crystal X-ray method. There are four sorption sites for CO 2 molecules in the three-dimensional channel system of the silicalite-1. Two of them are in the straight channel in disorder (STR1 and STR2), while the other sites are in the sinusoidal channel (SIN) and at the intersection (INT). Their occupancy factors indicate that a large portion of the CO 2 molecules are located in the straight channel. It is also revealed that the straight channel is the most favorable for CO 2 molecules as sorption sites.

Crystallography shows that with the smaller xanthate-bound methyl groups in Zn(S 2 COMe) 2 (dafone) ( 1 ) and Cd(S 2 COMe) 2 (dafone) ( 3 ) anti-parallel C=O…C=O interactions link molecules into dimers. These are further associated via π—π interactions into a supramolecular chain, and in the case of 3 into a supramolecular two-dimensional array via C—H…S contacts. Increasing the size of the organic residue, i.e. to ethyl and isopropyl in Zn(S 2 COEt) 2 (dafone) ( 2 ), Cd(S 2 COEt) 2 (dafone) ( 4 ) and Cd(S 2 CO-iPr) 2 (dafone) ( 5 ), does not allow for the formation of this supramolecular architecture. Instead, supramolecular chains are sustained by C—H…S and C—H…π(chelate) interactions (the latter exclusively in the case of 5 ). The presence of recognisable/significant π—π and C—H…S and C—H…π(chelate) interactions is not consistent amongst the series yet only two crystal packing patterns are noted depending on the presence of the C=O…C=O interactions. This observation points to the importance of overall crystal packing considerations of binuclear species in 1 and 3 , and mononuclear species in 2 , 4 and 5 .

Two d 10 metal coordination polymers, [Zn(CMTB) (bipy)] · (H 2 O) 2 (1) and [Cd(CMTB)(bipy)] · (H 2 O) 1.25 (2) (CMTB = 4-[(carboxymethyl) thio]-benzoic acid, bipy = 2,2′-bipyridine) were synthesized under mild mixed solvothermal conditions and characterized by single crystal X-ray diffraction and IR spectroscopy. Compound 1 crystallizes in monoclinic system, space group P 2 1 / n with cell parameters: a = 8.1083(16) Å, b = 17.194(3) Å, c = 28.646(6) Å, β = 97.96(3)˚ and Z = 8. It contains a one-dimensional (1D) chain structure that is further assembled into a two-dimensional (2D) network by the co-effects of the inter-chain C—H ··· O hydrogen bonds. Each Zn(II) is six-coordinated to four O atoms from two CMTB ligands, and two N atoms from the 2,2′-bipyridine forming a distorted octahedral coordination geometry. Compound 2 crystallizes in monoclinic system, space group P 2/ c with cell parameters: a = 19.656(4) Å, b = 10.716(2) Å, c = 19.455(4) Å, β = 94.10(3) and Z = 8. It displays two-dimensional framework and metal ion Cd(II) is octahedrally coordinated to four O atoms and two N atoms. Both Compound 1 and 2 are photoluminescent active and their emission properties were also studied.

Remarkable differences are observed in the molecular structures of Zn(S 2 COCH 2 Ph) 2 (dafone) ( 1 ) and Cd(S 2 COCH 2 Ph) 2 (dafone) ( 2 ); where dafone is 4,5-diazafluoren-9-one-N,N′. In 1 , an S,O mode of coordination of one of the xanthate ligands is observed, an orientation that facilitates the formation of intramolecular π…π interactions between the benzyl and dafone rings. The second xanthate ligand coordinates in an S,S mode and the dafone ligand is chelating. The resulting N 2 OS 3 donor set defines a distorted octahedral coordination geometry. A similar geometry is found in 2 but based on an N 2 S 4 donor set. Despite the different molecular structures, the global crystal packing patterns for 1 and 2 are almost identical, comprising layers.

The reported compound, {Na 2 [Cu 4 (HCOO) 2 (pa) 4 (CH 3 OH)] · CH 3 OH} n ( 1 , H 2 pa = 2-(hydroxyimino)propionic acid), is a sodium salt of an anionic coordination polymer, comprising rare-topology tetranuclear cluster units, linked through Cu–O bonds to form a polymeric chain. Each cluster unit comprises four Cu 2+ cations, chelating 2-(oxyimino)propionate ligands, two formate ligands and one terminal methanol ligand. The neighbouring polymeric chains contact through O–H…O hydrogen bonds and are interconnected by Na–O coordination bonds to form a three-dimensional network.