Simon P. Foxon

Nickel‐Assisted Carbon–Fluorine Bond Activation of 2,4,6‐Trifluoropyrimidine: Synthesis of New Pyrimidine and Pyrimidinone Derivatives

Rapid and regioselective activation of the C-F bond of 2,4,6-trifluoropyrimidine occurs on reaction with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) in the presence of PEt(3) to give 1, which can be converted into complex 2, containing a further N(3)-metalated pyrimidin-4-one unit. The novel pyrimidin-4-one 3 is released on protonation of 2.

Evolution of linear absorption and nonlinear optical properties in v-shaped ruthenium(II)-based chromophores

In this article, we describe a series of complexes with electron-rich cis-{Ru(II)(NH(3))(4)}(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF(6)(-) salts and characterized by using various techniques including (1)H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities beta have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) and pi --> pi* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant beta(0) responses as high as ca. 600 x 10(-30) esu. These pseudo-C(2v) chromophores show two substantial components of the beta tensor, beta(zzz) and beta(zyy), although the relative significance of these varies with the physical method applied. According to HRS, beta(zzz) dominates in all cases, whereas the Stark analyses indicate that beta(zyy) is dominant in the shorter chromophores, but beta(zzz) and beta(zyy) are similar for the extended species. In contrast, finite field calculations predict that beta(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand pi-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880-3891).

Combining Very Large Quadratic and Cubic Nonlinear Optical Responses in Extended, Tris-Chelate Metallochromophores with Six π-Conjugated Pyridinium Substituents

We describe a series of nine new complex salts in which electron-rich Ru(II) or Fe(II) centers are connected via pi-conjugated bridges to six electron-accepting N-methyl-/N-arylpyridinium groups. This work builds upon our previous preliminary studies (Coe , B. J. J. Am. Chem. Soc. 2005, 127, 13399-13410; J. Phys. Chem. A 2007, 111, 472-478), with the aims of achieving greatly enhanced NLO properties and also combining large quadratic and cubic effects in potentially redox-switchable molecules. Characterization has involved various techniques, including electronic absorption spectroscopy and cyclic voltammetry. The complexes display intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) bands, and their pi --> pi* intraligand charge-transfer (ILCT) absorptions in the near-UV region show molar extinction coefficients as high as ca. 3.5 x 10(5) M(-1) cm(-1). Molecular quadratic nonlinear optical (NLO) responses beta have been determined by using hyper-Rayleigh scattering at 800 and 1064 nm and also via Stark (electroabsorption) spectroscopic studies. The directly and indirectly derived beta values are very large, with the Stark-based static first hyperpolarizabilities beta(0) reaching as high as ca. 10(-27) esu, and generally increase on extending the pi-conjugation and enhancing the electron-accepting strength of the ligands. Cubic NLO properties have also been measured by using the Z-scan technique, revealing relatively high two-photon absorption cross sections of up to 2500 GM at 750 nm.

Nickel‐vermittelte Aktivierung einer C‐F‐Bindung von 2,4,6‐Trifluorpyrimidin: Synthese neuartiger Pyrimidin‐ und Pyrimidinonderivate

Spontan und regioselektiv wird eine C-F-Bindung in 2,4,6-Trifluorpyrimidin von [Ni(cod)2] (cod=1,5-Cyclooctadien) in Gegenwart von PEt3 aktiviert, wobei 1 entsteht. 1 kann in den Komplex 2 uberfuhrt werden, der eine N(3)-metallierte Pyrimidin-4-on-Einheit enthalt. Das freie Pyrimdin-4-on 3 bildet sich bei der Protonierung von 2.

SYNTHESES AND SINGLE-CRYSTAL X-RAY STRUCTURES OF A SERIES OF MONOSUBSTITUTED CIS,CIS-1,3,5-TRIAMINOCYCLOHEXANE-BASED COMPLEXES

The four triimine compds. cis,cis-1,3,5-tris[(E)-(X)-benzylideneamino]cyclohexane [X = H (1); 3-hydroxy (2); 3,5-dimethoxy (3); 4-acetamido (4)] were synthesized by the condensation of cis,cis-1,3,5-triaminocyclohexane with a substituted arom. aldehyde. Complexation of these ligands with metal salts (1 with Ni, Cu, and Zn salts; 2 and 3 with Cu salts; 4 with a Zn salt) causes a selective hydrolysis reaction producing new monoimine complexes. The resulting complexes were characterized by a combination of IR spectroscopy, elemental anal., mass spectrometry and, in the cases of the zinc complexes, 1H NMR spectroscopy. The structures of all six complexes are confirmed by single-crystal x-ray crystallog. studies. [on SciFinder(R)]

A selective uranium extraction agent prepared by polymer imprinting

Using a modified method in the preparation of an imprinted polymer, we report here the synthesis of a uranyl-imprinted copolymer of chloroacrylic acid and ethylene glycol dimethacrylate, which—after removal of the template—selectively extracts uranium from dilute aqueous solution over a range of +2, +3 and +4 competitor metal ions.

Syntheses and structures of M(L)(X)BPh4 complexes {M=Co(II), Zn(II); L=cis-1,3,5-tris[3-(2-furyl)prop-2-enylideneamino]cyclohexane, X=OAc, NO3}: structural models of the active site of carbonic anhydrase

The metal coordination geometries in the structures of the zinc(II) and cobalt(II) complexes of the ligand cis-1,3,5-tris[3-(2-furyl)prop-2-enylideneamino]cyclohexane (fr-protach) and with the anions nitrate and acetate are structural models for the active site of carbonic anhydrase. The acetate structures show a striking structural correlation with the metal coordination environments in the known bicarbonate forms of the enzyme. Such structures provide a basis for understanding the marked effect of different metal substitution on the catalytic rate of the enzyme.

Syntheses and structures of a range of metal complexes with the ligand cis,cis-1,3,5-(E,E)-tris(phenylpropenylideneamino)cyclohexane

The ligand cis,cis-1,3,5-(E,E)-tris(phenylpropenylideneamino)cyclohexane (Ph-protach) was coordinated with a range of metal salts. The products were characterised by IR and 1H NMR spectroscopies and FAB+MS. In addition, the complexes [Cu(Ph-protach)(η2-SO4)][Cu(Ph-protach)(η1-SO4)(CH3OH)], [Ni(Ph-protach)(Cl)]BPh4, [Zn(Ph-protach)(Cl)]BPh4 and [Cd(Ph-protach)(NO3)(CH3OH)]BPh4 were structurally analysed by single crystal X-ray diffraction. Each complex exhibits an N3 face-capping coordination geometry around the metal ion and a stereochemically-rigid hydrophobic cavity around the metal ions remaining coordination site(s).

Phenoxyl radical FeIII complex of cis,cis-1,3,5-tris(3′,5′-di-tert-butylsalicylaldimino)cyclohexane, spectro-electrochemical and structural studies

Complexation of cis,cis-1,3,5-tris(3′,5′-di-tert-butylsalicylaldimino)cyclohexane (H3tBu2saltach) with MIII (M = Fe and Ga) followed by subsequent one electron oxidation results in the formation of stable phenoxyl-radical complexes.

The synthesis and spectroscopic characterisation of chiral meso-tetraarylmetalloporphyrins bearing meso-pentafluorophenyl groups

The successful synthesis of 5,10,15,20-tetrakis[(R,R)-2,6-bis(1-phenylbutoxy)phenyl]porphyrin, with (R)-1-phenylbutoxy substituents on each of the eight ortho-positions, by a 2+2 approach viameso-[(R,R)-2,6-bis(1-phenylbutoxy)phenyl]dipyrromethane rather than a one-pot condensation of (R,R)-2,6-bis(1-phenylbutoxy)benzaldehyde with pyrrole, is described. The synthesis has also been modified using meso-(pentafluorophenyl)dipyrromethane to prepare four further chiral porphyrins containing one, two (cis and trans) and three pentafluorophenyls in place of the bis(phenylbutoxy)phenyl groups. The cross-coupling of the two dipyrromethanes with pentafluorobenzaldehyde gave as one of the products the unexpected cis-disubstituted 5,10-bis(pentafluorophenyl)-15,20-bis[(R,R)-2,6-bis(1-phenylbutoxy)phenyl]porphyrin. It seems likely that the formation of the latter compound involves the acid-catalysed reversion of the dipyrromethane synthesis. Both faces of each of the porphyrins are chiral and equivalent in this way the wasteful formation and time-consuming separation of atropisomers is avoided. Four iron(III) and one manganese(III) complex of these porphyrins have been prepared. The 1H and 19F NMR spectra of the series of porphyrin ligands reveal some interesting structure- and symmetry-dependent splitting patterns and trends which are used to confirm the identities of the compounds. In particular, the 1H NMR couplings of the β-pyrrole hydrogens are very diagnostic of the substitution patterns of the meso-aryl groups on the porphyrin ring.