Photosensitizers containing the 1,8-naphthyridyl moiety and their use in dye-sensitized solar cells

Using a Friedl?nder condensation approach, we prepared a series of 2-(pyrid-2'-yl)-1,8-naphthyridines containing a carboethoxy group appended at the 4- and 4'-positions. Complexation of these ligands with Ru(II) and NaNCS led to the complexes [Ru(L)2(NCS)2], and subsequent hydrolysis of the ester groups afforded the carboxylic acid dyes 13b-15b. The more delocalized and electronegative nature of the 1,8-naphthyridyl moiety lowers the energy of the ligand pi*-level and extends the absorption envelope of these complexes well into the red. The system lacking a 4-carboxypyridine moiety shows poor absorbance in the blue region of the spectrum. Solar cells involving thin films of anatase TiO2 impregnated with these dyes were prepared, and their photovoltaic performance was evaluated. The incident photon-to-current efficiencies in the region beyond 625 nm were considerably greater than those of the prototype N3 dye.     

A DFT study on the radical scavenging activity of juglone and its derivatives

The structural and electronic properties of juglone and its derivatives and their radicals were investigated at density functional level. The topology of electron density and the hydrogen bond properties of the studied structures were investigated using the Atoms in Molecules (AIM) theory. It turned out that the presence of the dihydroxy functionality increases the radical stability through hydrogen bond formation and favors hydrogen atom abstraction. The introduction of electron-donating groups for the molecules increases the activities of antioxidants. Moreover, juglone and its derivatives appear to be good candidates for the one-electron-transfer mechanism. Their planar conformation and the extended electronic delocalization between adjacent rings determine low ionization potential (IP) values, and it can be further improved by the introduction of the electron-donating groups for the molecules.     

Design and study of Bi[1,8]naphthyridine ligands as potential photooxidation mediators in Ru(II) polypyridyl aquo complexes

A series of 3,3'-polymethylene-bridged bi[1,8]naphthyridine (binap) ligands, 3a-c, are complexed with Ru(II) to afford [Ru(tpy)(3a-c)(H(2)O)](2+) where an uncomplexed nitrogen on 3a-c is situated so it can form a H-bond with the coordinated water. An additional complex involving [Ru(4'-NMe(2)tpy)(3b)(H(2)O)](2+) is also prepared. X-ray analyses of the [Ru(tpy)(3a,c)(H(2)O)](2+) complexes indicate well-organized H-bonds even when the binap is nonplanar. In an attempt to realize photooxidation, the effects of light, varying potential, and pH were examined. A Pourbaix diagram indicated that the oxidation potential decreased by approximately 0.5 V in the pH range of 1.9-11.6. The lowest-energy electronic absorption for the binap complexes involves the metal-to-ligand charge transfer to the binap ligand and is sensitive to ligand planarity. The absorbance shifted to a lower energy as the auxiliary ligand became a better donor (4'-NMe(2)tpy) or as the water was deprotonated. Acetonitrile was found to displace water most easily for the complex of 3c, where the ligand is the least planar. Despite promising features, photooxidation of the bound water was not observed.     

Phosphorus chemical shift tensors of phosphido ligands in ruthenium carbonyl compounds: (31)P NMR spectroscopy of single-crystal and powder samples and ab initio calculations

The phosphorus chemical shift (CS) tensors of several ruthenium carbonyl compounds containing a phosphido ligand, micro), bridging a Ru [bond] Ru bond were characterized by solid-state (31)P NMR spectroscopy. As well, an analogous osmium compound was examined. The structures of most of the clusters investigated have approximate local C(2v) symmetry about the phosphorus atom. Compared to the "isolated" PH(2)(-) anion, the phosphorus nucleus of a bridging phosphido ligand exhibits considerable deshielding. The phosphorus CS tensors of most of the compounds have spans ranging from 230 to 350 ppm and skews of approximately zero. Single-crystal NMR was used to investigate the orientation of the phosphorus CS tensors for two of the compounds, Ru(2)(CO)(6)(mu(2)-C [triple bond] C [bond] Ph)(mu(2)-PPh(2)) and Ru(3)(CO)(9)(mu(2)-H)(mu(2)-PPh(2)). The intermediate component of the phosphorus CS tensor, delta(22), lies along the local C(2) axis in both compounds. The least shielded component, delta(11), lies perpendicular to the Ru [bond] P [bond] Ru plane while the most shielded component, delta(33), lies perpendicular to the C [bond]P [bond] C plane. The orientation of the phosphorus CS tensor for a third compound, Ru(2)(CO)(6)(mu(2)-PPh(2))(2), was investigated by the dipolar-chemical shift NMR technique and was found to be analogous, suggesting it to be the same in all compounds. Ab initio calculations of phosphorus magnetic shielding tensors have been carried out and reproduce the orientations found experimentally. The orientation of the CS tensor has been rationalized using simple frontier MO theory. Splittings due to (99,101)Ru [bond] (31)P spin-spin coupling have been observed for several of the complexes. A rare example of (189)Os [bond] (31)P spin-spin splittings is observed in the (31)P MAS NMR spectrum of the osmium cluster, where (1)J((189)Os, (31)P) is 367 Hz. For this complex, the (189)Os nuclear quadrupolar coupling constant is on the order of several hundred megahertz.     

杭州城区的自然季节和天气类型

本文以杭州城区气象台站的观测资料为依据，运用综合气候学方法，将杭州城区划分为11个自然季节和31种天气类型.     

Boradigermaallyl: (4+3) Cycloaddition-Initiated Boron Insertion into Benzene

The 2π electron 1,3-dipole boradigermaallyl, valence-isoelectronic to an allyl cation, is synthesized from a bis(germylene). It reacts with benzene at room temperature by insertion of a boron atom into the benzene ring. Computational investigation of the mechanism shows the boradigermaallyl reacting with a benzene molecule in a concerted (4+3) or [π4s+π2s] cycloaddition reaction. Thus, the boradigermaallyl acts as a highly reactive dienophile in this cycloaddition reaction with nonactivated benzene as diene unit. This type of reactivity provides a novel platform for ligand assisted borylene insertion chemistry.     

Synthesis of Cobalt-Tin and -Lead Tetrylidynes—Reactivity Study of the Triple Bond

Tetrylidynes [TbbSn≡Co(PMe₃)₃] ( 1 a ) and [TbbPb≡Co(PMe₃)₃] ( 2 ) (Tbb=2,6-[CH(SiMe₃)₂]₂-4-(t-Bu)C₆H₂) are accessed for the first time via a substitution reaction between [Na(OEt₂)][Co(PMe₃)₄] and [Li(thf)₂][TbbEBr₂] (E=Sn, Pb). Following an alternative procedure the stannylidyne [Ar*Sn≡Co(PMe₃)₃] ( 1 b ) was synthesized by hydrogen atom abstraction using AIBN from the paramagnetic hydride complex [Ar*SnH=Co(PMe₃)₃] ( 4 ) (AIBN=azobis(isobutyronitrile)). The stannylidyne 1 a adds two equivalents of water to yield the dihydroxide [TbbSn(OH)₂CoH₂(PMe₃)₃] ( 5 ). In reaction of the stannylidyne 1 a with CO₂ a product of a redox reaction [TbbSn(CO₃)Co(CO)(PMe₃)₃] ( 6 ) was isolated. Protonation of the tetrylidynes occurs at the cobalt atom to give the metalla-stanna vinyl cation [TbbSn=CoH(PMe₃)₃][BAr^F₄] ( 7 a ) [Ar^F=C₆H₃-3,5-(CF₃)₂]. The analogous germanium and tin cations [Ar*E=CoH(PMe₃)₃][BAr^F₄] (E=Ge 9 , Sn 7 b ) (Ar*=C₆H₃(2,6-Trip)₂, Trip=2,4,6-C₆H₂iPr₃) were also obtained by oxidation of the paramagnetic complexes [Ar*EH=Co(PMe₃)₃] (E=Ge 3 , Sn 4 ), which were synthesized by substitution of a PMe₃ ligand of [Co(PMe₃)₄] by a hydridoylene (Ar*EH) unit.