N. Kent Dalley

The synthesis of azacrown ethers with quinoline-based sidearms as potential zinc(II) fluorophores

Abstract Two novel fluorophores, 12 and 13 , composed of diaza-18-crown-6 ligands containing two quinoline-based sidearms which are structurally similar to Zn(II) fluorophores TSQ ( 1 ) and Zinquin ( 2 ) were synthesized as potential Zn(II) fluorophores by reductive amination of 8-benzenesulfonamido-2-quinoline carboxaldehyde 6 and 8-benzenesulfonamido-6-quinolyloxyacetate-2-carboxaldehyde 11 with diaza-18-crown-6 using sodium triacetoxyborohydride (NaBH(OAc)3) as the reducing agent. Preliminary photophysical properties of ligands 12 and 13 show that they possess the properties necessary to be effective chemosensors for Zn2+. The solid state structure of 12 is also reported.

SYNTHESES, CRYSTAL STRUCTURES AND COORDINATION COMPOUNDS OF SOME 2-HETARYLCYANOXIMES

Abstract 2-hetarylcyanoximes which have the general formula HO–NC(CN)–R, where R is a heterocyclic group such as 2-pyridyl, 2-quinolyl, 2-benzthiazolyl etc., have been found to be good multidentate ligands for coordination chemistry. They form intensely colored complexes with iron(II) and bis-compounds with copper(I), which are used in analytical chemistry. Stability constants for anionic Fe2+ tris-cyanoximates were determined. The detailed syntheses and crystal structures of 2-pyridilcyanoxime (HPCO), 2-quinolylcyanoxime (HQCO) and 2-thiazolylcyanoxime (HTLCO) are reported. Molecules of HPCO in the crystal state adopt a non-planar cis–anti conformation. HQCO crystallizes as a monohydrate and this cyanoxime has a trans–anti non-planar conformation in the solid state. Molecules of HTLCO showed a trans–syn planar conformation in the solid state. Crystal structures of other known cyanoxime ligands are reviewed, as well as syntheses and the coordination modes for 2-hetarylcyanoximes in various complexes with s-, p- and d-metals.

Carbon-13 chemical-shift tensors in single-crystal methoxybenzenes

Using a two-dimensional NMR orientational correlation technique, carbon-13 chemical-shift tensors have been measured in single crystals of 1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene and 1,2,3-trimethoxybenzene. The two-dimensional technique greatly extends the single-crystal method to materials with a much larger number of different carbon-13 resonance lines. The manner of dealing with chemically identical, but magnetically inequivalent carbons in the unit cell is discussed. The X-ray structure of 1,2,3-trimethoxybenzene is reported for the first time, and a redetermination of the X-ray structure for 1,4-dimethoxybenzene is given. The principal values of all carbon-13 chemical-shift tensors in the three molecules and the orientation of their principal axes have been obtained. Using multiple regressional analysis the principal values of the tensors have been discussed in terms of additive substituent effects. Ab initio calculations of the shielding tensors in anisole (methoxybenzene) and benzene were used to calculate substituent effects which agree closely with the parameters obtained from the regressional analysis.

Azacrown ethers containing oximic and Schiff base sidearms - potential heteronuclear metal ion receptors

Abstract A simple synthetic pathway for the preparation of oxime- and Schiff base-containing aza- and diazacrown ethers is reported. N-Methoxymethyl-substituted aza-15-crown-5 and aza-18-crown-6 as well as N,N′-bis(methoxymethyl)-substituted diaza-18-crown-6 were treated with 5-bromosalicylaldehyde to produce the N-(2′-hydroxy-3′-carbonyl-5′-bromobenzyl)-substituted aza-15-crown-5 (8), aza-18-crown-6 (9) and N,N′-bis(2′-hydroxy-3′-carbonyl-5′-bromobenzyl)-substituted diaza-18-crown-6 (10) compounds. Compounds 8 and 10 were treated with hydroxylamine to give oxime-substituted ligands 12 and 13. A series of bis-Schiff base-containing diaza-18-crown-6 ligands were prepared by reacting 10 with 2-hydroxyaniline (to form 14), 5-nitro-2-hydroxyaniline (15), 2-aminopyridine (16), 2-hydrazinopyridine (17) and N-aminomorpholine (18). Compounds 12–18 are potential complexing agents for simultaneous binding of soft transition and hard alkali or alkaline earth metal ions in one molecule. These new oxime- and Schiff base-containing ligands interacted strongly with Na+ and K+ in methanol. The interaction of the aromatic portions of 9, 10, and 12–15 with transition metal ions was shown by the UV spectra of the metal ion complexes in 50% aqueous DMF. The X-ray structure of 10 is reported.

Short syntheses of triamine derivatives of cholic acid

Abstract Reduction of the trioxime derivative of dehydrocholic acid methyl ester with NaBH4TiCl4 yielded triamine-derivatives of cholic acid. The major product from the reduction was the 3α, 7α, 12α diastereomer. Stereochemistry of the reduction products was determined via NMR spectroscopy and X-ray crystallography.

Demetallation of a Ni(II) tetraazamacrocyclic complex by cyanoxime resulting in the formation of a stereospecific trinuclear compound [Na(H2O)6]+[NaNi2L6]− (L = NC-C(NO)-C(O)NH )

The reaction between the NiA(ClO4)2 and NaHL2 {where A = 14ane[N4], the macrocyclic ligands derived from the product of template condensation of 2,6-diacetylpyridine with aliphatic 3,3′-diaminodipropylamine, NH2(CH2)3NH(CH2)3NH2; and L = 2-cyano-2-isonitrosoacetamide anion, ACO− (amidecyanoxime, NC-C(NO)-C(O) )} has led to the formation of a highly unusual trimetallic bis-[ fac-(triscyanoximato) nickel(II)] anionic complex anion instead of the expected Ni(II) macrocyclic complex with coordinated cyanoxime ligands. Two equivalent and symmetric trigonal-prismatic NiL units are connected to form the [NaNi2L6]− anion by the presence of a central sodium cation. The latter is located between two NiL anions and has an octahedral NaO6 geometry comprised of oxygen atoms of the nitroso group of the cyanoxime ligand. The oxime ligand is planar and adopts a cis-anti configuration in the complex.

Improved and large-scale synthesis of certain glycosyl cyanides. Synthesis of 2,5-anhydro-5-thio-D-allononitrile.

The first synthesis of 2,5-anhydro-5-thio-D-allononitrile starting with L-lyxose, via a trifluoromethanesulfonic ester intermediate, has been accomplished. Methods have been developed to achieve a large-scale synthesis of 3,4,5,7-tetra-O-acetyl-2,6-anhydro-D-glycero-D-talo-heptononitrile (5). An improved procedure has been developed to synthesize 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulononitrile (9). The structures of 5 and the thioamide derivative from 9, 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulonothioamide, were confirmed by X-ray crystallographic analysis.

The double helical binuclear cooper complex of 6,6⁗ dimethyl-4′, 4‴ diphenyl-quinquepyridine and monohelical cadmium complex of 6,6⁗-dimethylquinquepyridine. Syntheses, crystal and molecular structure of [Cu2 (L2)2] [ClO4]3 · 2CH3CN and [CdL1] [ClO4]2

Abstract The binuclear copper complex of 6,6⁗-dimethyl-4′,4‴-diphenylquinquepyridine L2 and the mononuclear cadmium complex of 6,6⁗-dimethyl-quinquepyridine L1 have been prepared by the reaction of L2 with Cu(ClO4)2 · 6H2O and L1 with Cd(ClO4)2 · 2H2O, respectively. These complexes were characterized by elemental analysis, IR, 1H NMR and fast atom bombardment MS spectra. X-ray crystallographic measurement reveals that a Cu1 CuII mixed valence state copper complex is obtained, in which two ligand molecules self-organized around the CuI and CuII ions to form a double helical configuration. The cadmium complex is mononuclear, has a highly symmetrical configuration and may be regarded as a monohelical compound.

Syn-bishydroxymethyl-14-crown-4: A possible pre-organized molecule for simultaneous lithium complexation and anion solvation

Abstract The synthesis and molecular structure of syn-6,13-bishydroxymethyl-14-crown-4 is reported. Conformational analysis reveals that the gauche arrangement between the ethereal oxygens (-O-CH 2 CH 2 -O- units) is the preferred conformation. The CH 2 OH groups bonded to the ring, point away from the cavity and have a syn relationship. The synthetic route is elucidated by the crystal structure of 6,13-dimethylenyl-14-crown-4-LiSCN complex.

Novel syntheses of monofunctionalized triaza-crowns and cyclams with a secondary amine group on a side chain

Abstract Several monofunctionalized triaza-crowns and cyclams each containing a secondary amine group on a side chain have been prepared in good yields in few steps from readily available starting materials. The X-ray crystal structure of the complex of silver ion with 1-(2-ethylamino)ethyl-4,7,10,13-tetraethyl-1,4,7,10,13-pentaazacyclopentadecane (4) shows that the nitrogen atom of the side chain interacts strongly with the silver ion.