Biomedical subjects

M A Leech

Publications and source records attributed to M A Leech.

4 recordsLinked to original sources

PubMed2001

Hexahydroxybenzene-2,2'-bipyridine (1/2).

2,2'-Bipyridine (2BPY) and hexahydroxybenzene (HHB) crystallize in a 2:1 ratio as a neutral molecular adduct, C(6)H(6)O(6).2C(10)H(8)N(2), in space group P1 with Z = 1 and with the HHB molecule lying on an inversion centre. HHB, of which this is the first single-crystal X-ray structure determination, forms O-H...O hydrogen-bonded chains parallel to the a axis, with O...O distances of 2.761 (1) and 2.782 (1) A. O-H...N hydrogen bonds to the 2BPY molecules crosslink these chains, with O...N distances of 2.707 (1) and 2.735 (1) A.

Journal Article↗

PubMed2001

Interpenetrating supramolecular lattices in 4,4'-bipyridine-2,3,5,6-tetrahydroxy-1,4-benzoquinone (3/2).

4,4'-Bipyridine (BPY) and 2,3,5,6-tetrahydroxy-1,4-benzoquinone (THBQ) crystallize in a 3:2 ratio as a neutral molecular adduct, 3C(10)H(8)N(2).2C(6)H(4)O(6), in space group P1. There are two independent and centrosymmetric THBQ molecules and two different BPY molecules in the asymmetric unit, one of which lies about an inversion centre. The molecules link together through O-H...O and O-H...N hydrogen bonds to form three interpenetrating networks which create a 'superlattice' of three times the volume of the primitive cell.

Journal Article↗

PubMed2001

The 1:1 adduct of 2,5-dihydroxy-1,4-benzoquinone with 4,4'-bipyridine.

2,5-Dihydroxy-1,4-benzoquinone (DHBQ) and 4,4'-bipyridine (BPY) crystallize in a 1:1 ratio as a neutral molecular adduct, C(6)H(4)O(4).C(10)H(8)N(2), in space group C2/c, with half of each molecule in the asymmetric unit. The molecules are linked by a strong O--H...N hydrogen bond [O...N 2.6323 (15) A] and a weak C--H...O hydrogen bond [C...O 3.2082 (17) A] to form infinite stacks of parallel one-dimensional hydrogen-bonded ribbons. The two rings of the bipyridine are twisted at 28.3 degrees with respect to each other, and the benzoquinone ring is inclined at an angle of 18.3 degrees with respect to the plane of the neighbouring pyridine ring. The 4,4'-bipyridine molecule lies on a twofold axis and the benzoquinone molecule lies across an inversion centre.

Journal Article↗

PubMed2000

Uranium(VI) sulfilimine complexes: a new class of nitrogen analogues of the uranyl ion.

The compound tetraphenylphosphonium tetrachlorooxo-S,S-diphenylsulfiliminatouranium, [Ph4P][UOCl4(NSPh2)], has been prepared in high yield from [Ph4P][UOCl5] and [Ph2S=NSiMe3]. An X-ray structure of this compound shows that the uranium atom has a pseudooctahedral geometry with oxygen and nitrogen atoms in trans positions. The structure of the analogous phosphoriminato complex [Ph4P][UOCl4(NPPh3)] has been determined for comparison. Derivatization of the sulfide group shows that only a limited range of functionalization confers stability toward reduction. The emission spectrum of the first electronic excited state reveals a greatly reduced energy compared with that of the uranyl ion. This red shift in the transition is consistent with the weakening of the U-N bond relative to the U-O bond.

Journal Article↗