Biomedical subjects

Hugh D Selby

Publications and source records attributed to Hugh D Selby.

5 recordsLinked to original sources

PubMed2003

Hydrogen-bonded extended arrays of the [Re6(mu3-Se)8]2+ core-containing clusters.

Site-differentiated solvated clusters of the general formula [Re(6)(mu(3)-Se)(8)(PEt(3))(n)(MeCN)(6)(-)(n)](SbF(6))(2) (n = 4, cis and trans; n = 5) undergo ligand substitution reaction with isonicotinamide to afford the corresponding amide derivatives, [Re(6)(mu(3)-Se)(8)(PEt(3))(n)(isonicotinamide)(6)(-)(n)](2+) [1 (n = 5); 2 (n = 4, trans); 3 (n = 4, cis)]. Retention of stereochemistry in each case was confirmed by (1)H and (31)P NMR. The solid-state structures of all three compounds were established crystallographically, which revealed self-complementary hydrogen-bonding interactions between adjacent cluster units. While complex 1 exists as hydrogen-bonded dimers in the solid state, compounds 2 and 3 form one-dimensional chains of clusters bridged by paired hydrogen bonds. It is the rigid stereochemistry of the cluster, combined with the classic crystal engineering motif of complementary N-H.O amide hydrogen bonding, that affords the predictable solid-state structures and dimensionality.

Journal Article↗

PubMed2002

New oxovanadium bis(1,2-dithiolate) compounds that mimic the hydrogen-bonding interactions at the active sites of mononuclear molybdenum enzymes.

Reaction of VO(acac)(2) with 1,2-dithiols in the presence of triethylamine gives pentacoordinate oxovanadium complexes [HNEt(3)](2)[VO(bdt)(2)] (1), [HNEt(3)](2)[VO(tdt)(2)] (2), and [HNEt(3)](2)[VO(bdtCl(2))(2)] (3) (where H(2)bdt = 1,2-benzenedithiol, H(2)tdt = 3,4-toluenedithiol, and H(2)bdtCl(2) = 3,6-dichloro-1,2-benzenedithiol). Compounds 1-3 have been characterized by IR, UV/visible, EPR, and mass spectroscopies. The X-ray crystal stuctures of 1 and 2 show hydrogen-bonding interactions between the terminal oxo atom and triethylammonium counterions and between ligand sulfur atoms and the counterions. These interactions are comparable with those found at the active sites of mononuclear molybdenum enzymes.

Binding Sites↗

PubMed2002

Novel concentration-driven structural interconversion in shape-specific solids supported by the octahedral [Re(6)(mu3-Se)8]2+ cluster core.

A complex containing the face-capped octahedral [Re(6)(mu(3)-Se)(8)](2+) cluster core, cis-[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)](SbF(6))(2) (1), is used as a ditopic ligand with an enforced right angle between the two 4,4'-dipyridyl moieties for the coordination of Cd(2+) ion. Two coordination polymers, [[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)](2)[Cd(NO(3))(2)]](SbF(6))(4).21C(4)H(10)O.21CH(2)Cl(2) (2) and [[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)][Cd(NO(3))(3)]](NO(3)).2C(4)H(10)O.CH(2)Cl(2) (3), are obtained. The relative concentration of Cd(2+) determines which species is isolated, and the conversion of the first structure into the second is demonstrated experimentally.

Journal Article↗

PubMed2002

Built to order: molecular tinkertoys from the [Re(6)(mu(3)-Se)(8)](2+) clusters.

Ligand substitution of [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CH(3)CN)](SbF(6))(2) (1) with pyridyl-based ligands, 2,4,6-tri-4-pyridyl-1,3,5-triazine (L1) and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (L2), produced respectively the star-shaped tricluster (T1) and tetracluster (T2) arrays, wherein three (T1) and four (T2) units of the [Re(6)(mu(3)-Se)(8)](2+) core-containing clusters are interconnected by the corresponding bridging ligands. These novel supramolecular assemblies were characterized by a combination of NMR ((1)H and (31)P) spectroscopy, ESI-MS, and microanalysis. The molecular and solid-state structures of T1 have also been established by single-crystal X-ray diffraction.

Journal Article↗

PubMed2002

Halide-templated assembly of polynuclear lanthanide-hydroxo complexes.

A series of pentadecanuclear lanthanide-hydroxo complexes possessing a common core of the formula [Ln(15)(mu(3)-OH)(20)(mu(5)-X)](24+)(1, Ln = Eu, X = Cl(-); 2, Ln = Nd, X = Cl(-); 3, Ln = Gd, X = Cl(-); 4, Ln = Pr, X = Br(-); 5, Ln = Eu, X = Br(-)) were prepared by L-tyrosine-controlled hydrolysis of corresponding lanthanide perchlorates in the presence of added Cl(-) or Br(-). The cationic cluster core comprises five vertex-sharing cubane-like [Ln(4)(mu(3)-OH)(4)](8+) units centered on the halide template. In the case of templating I(-), dodecanuclear complexes were isolated instead. The core component, [Ln(12)(mu(3)-OH)(16)(I)(2)](18+) (6, Ln = Dy; 7, Ln = Er), consists of four vertex-sharing cubane-like [Ln(4)(mu(3)-OH)(4)](8+) units and exists as a square-shaped cyclic structure with one I(-) located on each side of the square plane. An analogous hydrolytic reaction involving Er(NO(3))(3), L-tyrosine, and NaOH affords the known hexanuclear complex [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))(2) whose core component is a face-capped octahedral [Er(6)(mu(6)-O)(mu(3)-OH)(8)](8+) cluster with an interstitial mu(6)-oxo group (Wang, R.; Carducci, M. D.; Zheng, Z. Inorg. Chem. 2000, 39, 1836-1837.). The efficient self-assembly of halide-encapsulating multicubane complexes (1-7) and the inability to produce an analogous nitrate-containing complex demonstrate the superior templating roles played by the halide ion(s). Further credence for the halide template effects was provided by the isolation of the cationic pentadecanuclear complex 3 as the sole product when tyrosine-supported hydrolysis of Gd(NO(3))(3) was carried out in the presence of competitive Cl(-). Magnetic moments of complexes 1-7 measured at room temperature by using Evans' method are in excellent agreement with those calculated by the Van Vleck equation, assuming magnetically noninteractive lanthanide ions.

Bromides↗