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2,6‐Bis(pyrrol‐2‐yl)pyridines are important building blocks for supramolecular assemblies and photoluminescent main group and transition metal compounds. Sterically encumbered 2,6‐bis(5‐(2,4,6‐trimethylphenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine, H2MesPDPPh, can adopt monomeric and dimeric structures in the solid state and in solution, controlled by competing inter‐ and intramolecular hydrogen bonds. Deprotonation in the presence of lithium cations provides Li2MesPDPPh, which can be isolated in monomeric and dimeric forms depending on solvent polarity. Protonation of H2MesPDPPh disrupts intramolecular hydrogen bonding and provides the monomeric pyridinium salt [H3MesPDPPh]Cl. Independent of solvent polarity, all three derivatives exhibit intense fluorescence in solution. The absorption and emission spectra are highly sensitive to the level of protonation, which can be rationalized by the effects of (de)protonation on the HOMO and LUMO of the tricyclic π‐system. [ABSTRACT FROM AUTHOR]

The photoluminescent eight-coordinate zirconium complex Zr(HPMPH)4 supported by four monoanionic 2-(2′-pyridine)pyrrolide ligands was synthesized. This molecule shows dual emission via fluorescence and phosphorescence with an overall quantum efficiency of 4% at room temperature in solution. The phosphorescence lifetime is dependent on concentration, indicating excimer formation at higher concentrations, and reaches almost 800 μs at high dilution. [ABSTRACT FROM AUTHOR]

A new metabolite of the biologically active thiocarbamide dimethylthiourea (DMTU) has been synthesized and characterized. DMTU's metabolic activation in the physiological environment is expected to be dominated by S- oxygenation, which produces, successively, the sulfenic, sulfinic, and sulfonic acids before forming sulfate and dimethylurea. Only the sulfinic and sulfonic acids are stable enough to be isolated. This manuscript reports on the first synthesis, isolation, and characterization of the sulfonic acid: dimethylaminoiminomethanesulfonic acid (DMAIMSOA). It crystallizes in the orthorhombic Pbca space group and exists as a zwitterion in its solid crystal form. The negative charge is delocalized over the sulfonic acid oxygens and the positive charge is concentrated over the planar N-C-N framework rather than strictly on the [sp.sup.2]-hybridized cationic carbon center. As opposed to its sulfinic acid analogue, DMAIMSOA is extremely inert in acidic environments and can maintain its titer for weeks at pH 6 and below. It is, however, reasonably reactive at physiological pH conditions and can be oxidized to dimethylurea and sulfate by mild oxidants such as aqueous iodine. Key words: thiourea, metabolites, bioactivation. On a effectue la synthase d'un nouveau metabolite du thiocarbamide de la dimeethylthioureee (DMTU), un produit biologiquement actif. On s'attend a ce que l'activation metabolique du DMTU dans un environnement physiologique devrait etre dominee par une S-oxygenation qui conduit a la formation successive d'acides sulfenique, sulfinique et sulfonique avant de donner un sulfate et de la dimethyluree. Seuls les acides sulfinique et sulfonique sont suffisamment stables pour etre isolees. Dans ce travail, on rapporte la premiere synthase, l'isolation et la caracteerisation de l'acide sulfonique, l'acide dime;thylaminoiminome;thanesulfonique (ADMAIMSO). Il cristallise dans le systeme orthorhombique, groupe d'espace Pbca et dans sa forme cristalline solide il existe sous la forme de zwitterion. La charge negative est deelocaliseee sur les oxygenes de l'acide sulfonique et la charge positive est concentree sur le squelette planaire N-C-N plutot que strictement sur le centre carbonee cationique d'hybridation [sp.sup.2]. Par opposition a son analogue l'acide sulfinique, le ADMAIMSO est extremement inerte dans des environnements acides et il peut maintenir son titre pour plusieurs semaines a des pH de 6 ou moins. Il est toutefois assez reactif dans des conditions de pH physiologique et il peut etre oxyde en dimeethyluree et en sulfate par des oxydants doux, tel une solution aqueuse d'iode. Mots-cles: thiouree, metabolites, bioactivation. [Traduit par la Redaction], Introduction N,N'-Dimethylthiourea (DMTU) is a well-known sulfur-based radical scavenger. (1-4) It is a small, highly diffusible molecule that efficiently scavenges toxic oxygen metabolites and reduces oxidative injury in many biologic [...]

The synthesis and characterization of a series of [Cu.sub.1] methyl, phenyl, anilido, ethoxide, and phenoxide complexes with the NHC ligands IPr, IMes [IMes = 1,3-bis(2,4,6-trimethylphenyl)imidiazol-2-ylidene], and SIPr [SIPr = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] are discussed. Details of characterization, solid-state structures, comparative relevant to the observed reactivity are provided.

The photochromic compounds trans- and cis-[Ru(tpy)(Mepic)(dmso)](OS[O.sub.2]C[F.sub.3]) [where tpy=2,2':6',2'-terpyridine; Mepic=6-methyl-2-pyridinecarboxylate; dmso=dimethyl sulfoxide] and cis-[Ru(tpy)(Brpic)(dmso)](P[F.sub.6]) [where Brpic=6-bromo-2-pyridinecarboxylate] were prepared and characterized. The methyl group promotes isomerization by hindering rotation of the dmso ligand about the Ru-S bond indicating that rotation is an important vibration for isomerization in photochromic Ru-dmso complexes.

Experimental evidence suggests that the hydrogen-deuterium exchange reactions occur through Ru-mediated activation of arene C-D bonds. The results suggest that net 1,2-addition of C-H bonds across late transition metal oxygen or nitrogen nondative bonds is kinetically accessible, and for the Ru systems is more rapid than analogous reactions with alkyl or aryl ligands.

Abstract: One of the major metabolites of dimethylthiourea, dimethylaminoiminomethanesulfinic acid (DMAIMSA), was synthesized by controlled oxidation of dimethylthiourea using hydrogen peroxide. The crystal structure was determined by X-ray crystallography. It [...]

Investigations indicate that dmso isomerization in ruthenium occurs within a strong-field ligand environment. Isomerization in these complexes occurs following format ion of an equilibrated S-bonded excited state.

A study shows that benzannulated enyne-allenes bearing a heteroaromatic substituent at the allenic terminus are excellent precursors of a variety of indeno-fused heteroaromatic ring systems. The resulting heteroaromatic compounds are of interest as potential candidates for pharmacological applications.

The studies shows that the metal-based nucleophilicity provide a foundation for reactions of substrates that possess polar bonds with the Ru(II); amido complex (PCP)Ru(CO)(PMe3)(NHPh)(PCP = 2,6-(CH2P(super t)Bu2)2C6H3). The findings shows that reactions with substrates possessing C--X multiple bonds (X = O or N) results in the formation of heterometallacycles.

Research has been conducted on the pyrido[1',2':1,2]pyrimido[4,5-b]indoles and related pyrazino[1',2':1,2]pyrimido[4,5-b]indoles. The synthesis of these compounds has been carried out via the treatment of benzannulated enyne-isocyanates with the iminophosphoranes and the details are reported.

Research has been conducted on the heterocyclic aromatic compounds. The synthetic pathway to these compounds developed via the use of benzannulated enyne-carbodiimide thermolysis is described.

Research has been conducted on the 4,5-diarylphenanthrenes. The synthetic pathway to these diarylphenanthrenes which have a helical twist in their structure has been developed and the results indicate that the synthetic sequence involves diketone condensation with lithium acetylides derived from the diacetylenes followed by protonation in producing propargylic alcohols.

Research has been conducted on the 11H-benzo[b]fluoren-11-ols, 1H-cyclobut[a]indenes and related compounds. The synthetic pathway to these compounds has been developed using biradicals generated from benzoenyne-allenes and the results are presented.

Research has been conducted on the ligands in palladium/ligand-catalyzed Suzuki reactions. The authors discuss a catalyst for general Suzuki reactions.

Research was conducted to examine the use of a continuous flow pyrolysis reactor for the production of MoS2 using controlled gas phase decomposition of Mo(CO)6 and H2S. Yields were optimized while the surface area, crystallographic phase and chemical composition of the GPD products were influenced by varying the furnace temperature, the carrier gas flow, the gas injection type and the Mo(CO)6/H2S composition. Results indicate that the mass density of active sites was in proportion to surface areas of the materials.

The reaction of (Cp*RuCl)4 (Cp* = n(super 5)-C(sub 5)Me(sub 5)) with the carbene ligand 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) has been studied. The product of the reaction is an unsaturated Cp*Ru(IMes)Cl complex with an 86% isolated yield. The nucleophilic carbene IMes function as a tertiary phosphine analogue resulting in reaction enthalpies that are 5kcal/mol exothermic than those with PCy3 in the Cp*Ru(L)Cl system. Their steric properties are also more demanding than those of PCy3.

The thermally-induced isomerization of benzoenyne-allenes leads to the formation of two stable triarylmethyl radical centers. The resulting reaction is preceded by the formation of biradicals and is followed by the intramolecular trapping of a tetraarylallene. The experiment has also determined that the five-membered ring present in the fluorene system is essential in leading the reaction into the Myers cycloaromatization pathway.

5,6-Diaryldibenzo{a,e}cyclooctenes (sym-dibenzocyclooctatetraenes) were synthesized from (Z,Z)-1-aryl-3,5-octadiene-1,7-diynes. (+-)-(3R,4S,5Z)-3-(tert-butyldimethylsilyl)-6-methyl-1-(trimethylsilyl)-5-oc tene-1,7-diyn-4-ol was used as a latent moiety to enable cross-coupling with aryl iodides. The approach allowed easier access to a wide array of dienediynes for eventual transformation to 5,6-diaryldibenzo{a,e}cyclooctenes.

The X-ray crystal structures of the difluoro(porphyrinato)silicon(IV) complexes of tetra-p-tolylporphyrin were analyzed to determine their reactivity with hexacoordinate difluorosilanes. The (Por)SiF2 (Por = TTP, TTFP) exhibited Si-F bond lengths that were similar to cis- and trans-difluorosilanes. Furthermore, (TPP)SiF2 exhibited nucleophilic substitution due to the trans geometry of its fluoride units.

An alternative synthetic routes to enyne-allenes containing two phenyl substituents at the allenic end is described. The procedure, which is based on the Horner reaction between enynyl aldehydes and a phosphinoxy carbanion derived from dipheny(2,2-dipphenyl-1-iodoethenyl)phosphine oxide, produces alpha,3-didehydrotoluene biradicals with a stabilized triarylmethyl radical center and a reactive aryl radical center when concluded with the thermolysis of the resulting enyne-allenes in the presence of 1,4-cyclohexadiene.

An efficient route to chiral ansa-metallocenes of the type rac-(EBI)ZrX2 where (EBI = ethylene-1,2-bis 1-indenyl) and (X = NMe2,Cl,Me) was developed. The procedure is stereoselective because it involves a reversible amine elimination reaction in toluene between the amide Ze(NMe2)4 and (EBI)H2, otherwise known as 1,2-bis 3-indenyl(ethane). Moreover, the ratio of the rac-(EBI)Zr(NMe2)2 to the meso-(EBI)Zr(NMe2)2 products may be controlled by modifying the reaction conditions.

Examination of the nickel complex of the macrocyclic ligand, 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione (L), shows that it is incapable of cleaving methyl coenzyme-M (CoM) to methane. X-ray crystallographic studies characterize the structure of NiL(OAc)2 prepared from L synthesized from pure tetren. The nickel complex of 1,4,7,10-tetraazacyclotridecane-11,13-dione (L'), NiH-2L' also does not cleave methyl CoM. Solutions of physical mixtures of NiL(OAc)2 and NiH-2L' reproduce the observed spectra, but cannot carry out the cleavage reaction.

The cobalt-assisted Claisen rearrangement of complexed silyl ketene acetals, obtained from diastereoisomeric lactones, gives an 11-membered enediyne alcohol (4). The reaction gives high yields at ambient temperature. The propargylic rearrangement of 4 produces enyne allene that may undergo Myers cycloaromatization to give a seven-membered benzannulated ring system stereoselectively. The lactone preparation involves the use of the corresponding hydroxy acids.

X-ray diffraction studies help compare the structures of the Co(OEP)CH3, Co(OEP)(CH3)(Py) and Co(OEP)(DMAP) complexes. Electronic trans interaction of pyridine and steric interaction of alkyl ligand with porphyrin increases Co-C bond length in Co(OEP)(CH3)(Py) when compared to Co(OEP)(CH3). The steric interaction is higher in Co(OEP)(CH3)Py than in Co(OEP)(DMAP), which is produced by homolysis. Reduced Co-N(ax) distance after homolysis reveals the stronger ligand binding in the five-coordinate complex than in the six-coordinate complex.

The factors that influence the conformation of anhydrides were studied. UV-VIS spectral analysis of anhydrides was done in benzene and THF and structures were determined using X-ray crytallography. Anhydrides with small substituents preferred the syn- or the anti-conformation of the carbonyl groups. Dihedral angles were found to increase while minimum energies were similar. Results showed that the gas phase structure became more twisted as a result of increased steric demands. These changes caused significant alterations in the reduction potential and UV-VIS spectra.

The crystal structures of palladium(II) octaethylporphyrin, palladium(II) trans-octaethylchlorin and palladium(II) tct-octaethylisobacteriochlorin are examined for their differences. These palladium(II) complexes form a homologous series of square-planar complexes, and show differences in structural arrangements and macrocycle conformations. The crystal densities of the structures decrease with increasing macrocycle saturations.