Lambda-[1,4,7,10-tetrakis[(S)-2-hydroxypropyl-kappaO]-1,4,7,10-tetraazacyclododecane-kappa4N]cadmium(II) bis(2,4,6-trinitrophenolate) acetonitrile solvate.

Crystallization of [Cd(S-thpc12)](ClO(4))(2) x H(2)O [S-thpc12 is 1,4,7,10-tetrakis[(S)-2-hydroxypropyl]-1,4,7,10-tetraazacyclododecane] in the presence of two equivalents of sodium picrate monohydrate (sodium 2,4,6-trinitrophenolate monohydrate) diastereoselectively produces a neutral receptor complex, viz. the title compound, lambda-[Cd(C(20)H(44)N(4)O(4))](C(6)H(2)N(3)O(7))(2) x CH(3)CN. In this complex, two picrate anions hydrogen bond, via their phenolate moieties, to the pendant hydroxyl groups of the receptor which, together with the four N atoms, themselves bond to Cd(II) in an approximately cubic arrangement. One picrate anion hydrogen bonds to all four hydroxyl groups, one of which also acts as the sole hydrogen-bond donor to the second picrate anion.

On the structure of aragonite -- Lawrence Bragg revisited.

The structure of aragonite was first determined by Lawrence Bragg in 1924 in what is the now standard space-group setting Pnma (No. 62). Subsequent studies have all taken his structure as their starting points, despite Bragg's own stated doubts and some earlier etching studies which indicated that the underlying symmetry may really be polar. We have reinvestigated the structure and found that there are many reflections with significant intensity among those that should be systematically extinct in Pnma. Some of these reflections have been subjected to further experimental analysis and have been shown not to be due to Renninger effects. A possible model that satisfies these observations is one where the true structure is in space group P1; and the structure is twinned about the three axial twofold rotation axes of Pnma. The space group P1 cannot be ruled out. Evidence for these conclusions is presented. The crystal chemistry of aragonite is revisited and described in terms of the stuffed alloy CaC. The carbonate group is confirmed to be non-planar in the crystal.

Metal ion-dependent molecular inclusion chemistry: inclusion of aromatic anions by coordinated 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane.

The ability of the pendant donor macrocyclic ligand 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraaza- cyclododecane((S)-thphpc12) (or [Cd((S)-thphpc12)](2+)) to act as a metal ion-dependent receptor for aromatic anions has been investigated in solution and in the solid state. [Cd((S)-thphpc12)](2+) adopts a stable conical conformation with a large hydrophobic cavity, which has been shown to contain, via complementary multiple hydrogen bonding, p-nitrophenolate, aromatic carboxylates, p-toluenesulfonate, certain aromatic amino acid anions, phenoxyacetate, and acetate. In the case of p-nitrophenolate only, one or two anions can be contained within the receptor cavity. The crystal structure of [Cd((S)-thphpc12)(p-nitrophenolate)(2)] shows a coplanar arrangement of the p-nitrophenolates, where each is retained in the cavity by a pair of hydrogen bonds to cis hydroxyl groups. The crystal structure of the p-aminobenzoate inclusion complex indicates retention of the guest via a pair of hydrogen bonds to each oxygen atom of the carboxylate moiety. The crystal structure of the (L)-phenylalaninate inclusion complex indicates that the amino acid is retained by five hydrogen bonds, two involving the nitrogen atom and three to the oxygen atoms of the carboxylate moiety. Binding constants (10(3)-10(5) M(-1)) for the inclusion of some of the aforementioned anions in [Cd((S)-thphpc12)](2+) and related receptors were measured by (1)H NMR titration in DMSO-d(6) at 298 K.

Metal Ion Dependent Molecular Inclusion Chemistry: Inclusion of p-Toluenesulfonate and p-Nitrophenolate within the Structure of Coordinated 1,4,7,10-Tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane.

The pendant donor macrocyclic ligand 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane ((S)-thphpc12) has been synthesized in quantitative yield from cyclen (1,4,7,10-tetraazacyclododecane) and (2S)-(+)-3-phenoxy-1,2-epoxypropane. An X-ray diffraction study supports the result of molecular orbital calculations in showing that complexation with hydrated cadmium(II) diperchlorate produces an approximately square-antiprismatic complex in which the metal ion is located between a plane containing the four nitrogen atoms and a plane containing the four oxygen atoms. As a consequence of this the four phenoxymethyl moieties, each attached to one of the four N-O chelate rings, juxtapose to form a substantial empty cavity allowing the complex to act as a molecular receptor. Inclusion complexes have been formed from this complex in which either a p-toluenesulfonate or p-nitrophenolate anion has entered the cavity. An X-ray crystallographic study of [Cd((S)-thphpc12)(p-toluenesulfonate)]ClO(4) shows that the guest anion is retained within the cavity by four hydrogen bonds to the group of hydroxyl moieties associated with the ligand. (13)C NMR and conductivity studies indicate that this inclusion complex retains its integrity in DMSO or DMF solution. Parallel studies have been conducted with [Pb((S)-thphpc12)](ClO(4))(2) indicating that the corresponding inclusion complexes are of lower stability.

Gold(I)-Purine Interactions: Synthesis and Characterization of Cyclic and Open Chain Polynuclear Gold(I) Complexes Containing Xanthine Derivatives and Bis(phosphine) as Bridging Ligands. Crystal Structures of [Au(2)(&mgr;-HX)(&mgr;-dmpe)].3H(2)O and [Au(2)(&mgr;-TT)(&mgr;-dmpe)].H(2)O (H(3)X = Xanthine; H(2)TT = 8-Mercaptotheophylline).

The reaction of [(AuBr)(2)(&mgr;-PR(2)P(CH(2))(n)()PR(2))] (where R = CH(3) for n = 1; R = Ph for n = 1, 3, 4) with N-alkylxanthine and thioxanthine derivatives, containing two ionizable protons in close positions, yields, under basic conditions, neutral heterobridged dinuclear gold(I) ring complexes [Au(&mgr;-L)(2)(&mgr;-PR(2)P(CH(2))(n)()PR(2))], which have been investigated by means of (1)H- and (31)P-NMR and FAB spectroscopies. Crystal structures of two of these complexes are reported. [Au(2)(&mgr;-HX)(&mgr;-dmpe)].3H(2)O (1) (H(3)X = xanthine; dmpe = 1,2-bis(dimethylphosphine)ethane) crystallizes in the monoclinic space group P2(1)/n with a = 9.348(2) Å, b = 8.656(2) Å, c = 24.585(5) Å, beta = 98.24(2) degrees, Z = 4, and R = 0.040. [Au(2)(&mgr;-TT)(&mgr;-dmpe)].H(2)O (2) crystallizes in the monoclinic space group P2(1)/n with a = 10.853(4) Å, b = 14.031(6) Å, c = 13.574(5) Å, beta = 100.80(4) degrees, Z = 4, and R = 0.063. The structures of 1 and 2 are similar and consist of dinuclear nine-membered ring molecules, in which the two linear two-coordinate gold atoms are bridged on one side by a dmpe ligand and on the other side by a bidentate xanthinato dianion, with intramolecular Au.Au distances of 3.053(1) and 2.952 (2) Å, respectively. In the former, the coordination of the xanthinato ligand to the gold atoms takes place through the N3 and N9 nitrogen atoms whereas, in the latter, N7,S8-chelate coordination of the 8-thiotheophyllinato dianion occurs. The magnitude of the Au.Au separation is analyzed in terms of the twisting of the xanthine derivative ligand from the plane containing the gold(I) and phosphorus atoms. For n = 6 the steric requirements of the Au(&mgr;-dpph)Au group prevents the formation of dinuclear ring complexes and open chain complexes are obtained. Finally, when the xanthine derivatives do not contain two close active coordination sites dinuclear open chain complexes are formed.