Search results for "Benzene"

Design, synthesis and spectral studies of novel bile acid-arene conjugates: Trans to cis isomerization of azobenzene core controlled by bile acid hyd…

2008

Abstract Four bile acid-arene conjugates, 1,4-bis[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene dibromide ( 1 ), 1,3,5-tris[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene tribromide ( 2 ), bis{4-[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 3 ), and bis{4-[dimethyl(3α-hydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 4 ), have been synthesized in good yields, and their structures have been characterized by 1 H, 13 C, 13 C DEPT-135, PFG 1 H, 13 C HMQC, PFG 1 H, 13 C HMBC, and PFG 1 H, 15 N HMBC NMR spectra. Their molecular weights and elemental compositions have…

NMR studies on [Rh(η6-arene)(P(OPH)3)2]ClO4 in the presence of acetone-d6. Arene dissociation and dynamic behaviour of the solvent complex

1985

Abstract Dissociation of the complexes [Rh(η 6 -arene)L 2 ]ClO 4 (arene = mesitylene (Ia), toluene (Ib) and benzene (Ic); L = P(OPh) 3 ) with loss of the arene ligand in CD 2 Cl 2 / acetone- d 6 (95/5 mol/mol) has been studied by 31 P NMR spectroscopy; for initial 0.025 M concentrations of degrees of dissociation were 0.23, 0.33 and 0.85, respectively. The dissociations were first-order, with half-lifes of 31 (Ia), 1.2 (Ib) and 0.7 (Ic) h. The solvent complex [Rh(acetone) m L 2 ]ClO 4 produced by these dissociation reactions showed unusual dynamic structural behaviour. In dry acetone the two phosphorus nuclei were magnetically equivalent (species II-A 2 ), whereas in acetone solutions conta…

Dinuclear Ortho-Metalated Palladium(II) Compounds with N,N- and N,O-Donor Bridging Ligands. Synthesis of New Palladium(III) Complexes

2011

New dinuclear ortho-metalated palladium(II) compounds with N,N′-diarylformamidinates, Pd2[(C6H4)PPh2]2[R′NC(H)NR′]2 (R′ = C6H5, 3a; R′ = p-CH3C6H4, 3b; R′ = p-CH3OC6H4, 3c) and N,O-donor ligands, Pd2[(C6H4)PPh2]2[N,O]2 (N,O = succinimidate (5), phtalimidate (6), 2-hydroxypyridinate (7), acetanilidate (8)) have been synthesized and characterized by NMR spectroscopy and X-ray diffraction methods. The oxidation with iodobenzene dichloride gave new and rare Pd26+ compounds, Pd2[(C6H4)PPh2]2[R′NC(H)NR′]2Cl2 (R′ = C6H5, 4a; R′ = p-CH3C6H4, 4b). DFT calculations on the Pd24+ → Pd26+ oxidation reaction show that the substituents on the amidinate N atoms have a greater effect on the reaction energy …

Investigations on organotin, organolead, lead(IV), and lead(II) dithiolates

1985

Abstract Bis(triorganometal) 1,2-dithiolates (R3M)2S2R′ [(HS)2R′ = C7H8S2 for toluene-dithiol-3,4 (H2TDT); M = Sn, Pb; R = Ph; or (HS)2R′ = C10H14S2 for 1,2-dimethyl-4,5-bis(mercaptomethyl)benzene (H2DBB); M = Sn, R = CH3, C6H5; M = Pb, R = C6H5], diorganometal 1,2-dithiolates R2MS2R′ [(HS)2R′ = C6H6S2 for 1,2-dimercaptobenzene (H2DMB); M = Pb, R = CH3, C2H5, C6H5; or (HS)2R′ = H2TDT; M = Sn, R = CH3, C6H5; M = Pb, R = C6H5; or (HS)2R′ = H2DBB; M = Sn, R = CH3, C6H5; M = Pb, R = CH3, C2H2, C6H5; or (HS)2R′ = C8H6N2S2 for 2,3-dimercaptoquinoxaline (H2QDT); M = Pb, R = C6H5] and some lead(IV) and lead(II) dithiolates Pb(S2R′)n [(HS)2R′ = H2DMB, n = 2; (HS)2R′ = H2TDT, n = 2; (HS)2R′ = H2DBB, …

Antibodies directed to drug epitopes to investigate the structure of drug-protein photoadducts. Recognition of a common photobound substructure in ti…

2001

Drug-induced photoallergy is an immune adverse reaction to the combined effect of drugs and light. From the mechanistic point of view, it first involves covalent binding of drug to protein resulting in the formation of a photoantigen. Hence, determination of the structures of drug-protein photoadducts is of great relevance to understand the molecular basis of photoallergy and cross-immunoreactivity among drugs. Looking for new strategies to investigate the covalent photobinding of drugs to proteins, we generated highly specific antibodies to drug chemical substructures. The availability of such antibodies has allowed us to discriminate between the different modes by which tiaprofenic acid (…

Synthesis and characterization of cyclometallated palladium(II) complexes with 2-(diphenylphosphino)benzaldehyde

2013

New palladium(II) complexes containing 2-(diphenylphosphino)benzaldehyde a (Ph2P(o-C6H4CHO), displaying different coordination modes, have been synthesized in moderate to good yields (62–91%). The cyclometallated palladium(II) complexes [Pd(C^N)(Ph2 P(o-C6H4CHO)(Cl)] (1–4) in which a is P-monodentate have been prepared by reacting it with selected cyclometallated precursors containing bridging chlorides [Pd(C^N)(μ-Cl)]2 [C^N=2-phenylpyridine (Phpy), 7,8-benzoquinoline (Bzq), azobenzene (Phazo), and 2-phenyloxazoline (Phox), respectively]. A rigid P,O-chelating behavior of a, confirmed by the crystal structure determination of [Pd(Phox)(Ph2 P (o-C6H4CHO)][CF3SO3] (8), is observed in complexe…

1980

Formation and behaviour of radiation induced free radicals in statistical copolymers from vinyl hydrosulfide and styrene (1:1, 1:4, and 1:10) were investigated by means of ESR spectroscopy. The corresponding homopolymers were also included in these studies. After γ-irradiation of the copolymers at 77 K and subsequent annealing to 293 K it was possible to detect thio radicals. Their relative yields were found to increase with increasing styrene content. Investigations regarding the thermal behaviour of the radiation induced radicals in the copolymers allowed the assumption of two mechanisms responsible for the formation of the thio radicals: First, the formation takes place via ion radicals …

Two strained hexahelicenophanes

2000

The crystal structures of the [6]­helicenes 4,13-(1,10-deca­methyl­ene­dioxy)­hexahelicene, C36H34O2, (I), and 4,13-(1,8-octa­methyl­ene­dioxy)­hexahelicene, C34H30O2, (II), show strong steric interactions between the terminal benzene rings and the poly­methyl­ene­dioxy chains. The shortest ring A and F distances amount to 2.941 (3) and 2.902 (3) A, respectively. The increased steric energy of the ground state is responsible for a significantly lower racemization barrier of (I) and (II) in comparison to the unsubstituted [6]­helicene.

Unveiling the regioselectivity in electrophilic aromatic substitution reactions of deactivated benzenes through molecular electron density theory

2021

The origin of the meta regioselectivity in electrophilic aromatic substitution (EAS) reactions of deactivated benzene derivatives is herein analysed through Molecular Electron Density Theory (MEDT). To this end, the EAS reaction of benzenesulfonic acid with the nitronium NO2+ ion in H2SO4 solution has been studied at the ωB97X-D/6-311G(d,p) level. This reaction takes place through a two-step polar mechanism involving the formation of an unstable cation intermediate. The activation Gibbs free energies associated with the three competitive regioisomeric reaction paths are found in the narrow range of 15.5–18.3 kcal mol−1. By using the Eyring–Polanyi equation a relationship of 18.7 (ortho) : 8…

Valence Topological Charge-Transfer Indices for Reflecting Polarity: Correction for Heteromolecules

2005

Valence topological charge-transfer (CT) indices are applied to the calculation of dipole moments mu. The mu calculated by algebraic and vector semisums of the CT indices are defined. The model is generalized for molecules with heteroatoms and corrected for sp(3)-heteromolecules. The ability of the indices for the description of the molecular charge distribution is established by comparing them with mu of the valence-isoelectronic series of cyclopentadiene, benzene and styrene. Two CT indices, mu(vec) (vector semisum of vertex-pair mu) and mu(vec)V (valence mu(vec)) are proposed. The mu(vec) behaviour is intermediate between mu(vec) and mu(experiment). The correction is produced in the corr…