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941.
Steed JW Goeta AE Lipkowski J Swierczynski D Panteleon V Handa S 《Chemical communications (Cambridge, England)》2007,(8):813-815
Templation of a daughter phase by a parent crystal results from an equilibrating mixture of two very different copper(ii) N,N',N'-trimethyltriazacyclononane complexes. 相似文献
942.
Shannon J Bernier D Rawson D Woodward S 《Chemical communications (Cambridge, England)》2007,(38):3945-3947
Addition of AlMe3 to commercial THF solutions of RZnX (R = aryl, functionalised aryl, vinyl; X = Br, I) simultaneously promotes Schlenk equilibria (leading to competent nucleophiles) and the formation of an Al-Zn-ligand catalyst delivering 80-90% ee for Ar(1)CH(OH)Ar(2) formation from aldehydes. 相似文献
943.
Torres T Gouloumis A Sanchez-Garcia D Jayawickramarajah J Seitz W Guldi DM Sessler JL 《Chemical communications (Cambridge, England)》2007,(3):292-294
A new non-covalent electron transfer model system, based on the use of cytidine-guanosine hydrogen bonding interactions, is described that incorporates a phthalocyanine photodonor and a C60 fullerene acceptor. 相似文献
944.
DFT computed transition states quantitatively explain the surprising stereochemical outcome of unsubstituted enolborinates in diastereoselective and enantioselective boron aldol reactions. 相似文献
945.
Selby JD Manley CD Feliz M Schwarz AD Clot E Mountford P 《Chemical communications (Cambridge, England)》2007,(46):4937-4939
Two broadly applicable strategies for extending the available ligand platforms of the virtually unexplored terminal Ti=N-NR2 functional group are described, along with the highly selective room temperature insertion of alkynes into the N-N bond of Ti{MeN(CH2CH2NSiMe3)2}(NNPh2)(py) and the catalytic cis-diamination of PhC[triple bond]CMe by diphenylhydrazine. 相似文献
946.
Asymmetric ruthenium(II) complexes of a flexible aminomethylpyridine derivative exhibit diastereotopic ligand methylene protons, as measured by NMR spectroscopy; binding of external anions renders these protons equivalent possibly by increasing dynamically averaged symmetry; the amount of anion needed to raise average symmetry correlates to the anion binding constant. 相似文献
947.
Yang J Alemany LB Driver J Hartgerink JD Barron AR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(9):2530-2545
A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4'-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. 1H and 13C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-phase peptide synthesis. The presence of the C60-substituted amino acid in a peptide has a significant effect on the secondary structures and self-assembly properties of peptides as compared to the native peptide. The antioxidant assay of Baa and a Baa-derived anionic peptide was determined to be significantly more potent than Trolox. 相似文献
948.
Schumacher AL Sandanayaka AS Hill JP Ariga K Karr PA Araki Y Ito O D'Souza F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(16):4628-4635
By adopting a "covalent-coordinate" bonding approach, novel supramolecular pentad and triad molecules composed of zinc-porphyrin(s), fullerene(s), and oxoporphyrinogen redox-/photoactive entities have been constructed, and also characterized by means of spectral and electrochemical techniques. The geometry and electronic structures of the pentad and the triad were deduced by means of DFT calculations. Free-energy calculations suggested that the photoinduced electron/energy transfer from the zinc-porphyrin (ZnP) singlet-excited state to the imidazole modified fullerene (ImC(60)) acceptor and oxoporphyrinogen (OxP) entities is feasible for both the triad and the pentad. The charge-separation rates (k(CS)) determined from picosecond time-resolved emission studies were higher for pentad (C(60)Im:ZnP)(2)-OxP than for the corresponding triad, C(60)Im:ZnP-OxP. A comparison of the k(CS) values previously reported for the covalently linked bis(zinc-porphyrin)-oxoporphyrinogen triad suggests that employing a fullerene acceptor improves the electron-transfer rates. Nanosecond transient absorption studies provide evidence for the occurrence of electron-transfer processes. Lifetimes of the radical ion pairs (tau(RIP)) are in the range of hundreds of nanoseconds, which indicates that there is charge stabilization in the supramolecular systems. 相似文献
949.
Xie Y Hill JP Schumacher AL Karr PA D'Souza F Anson CE Powell AK Ariga K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(35):9824-9833
A novel corrole-type macrocycle, oxocorrologen (2), substituted with hemiquinone groups, has been synthesized. It was found to undergo multiple tautomerism of its exchangeable protons between electronegative atom sites at the macrocyclic core (nitrogen atoms) and periphery (phenol oxygen atoms). Alkylation at one macrocyclic nitrogen atom with a 4-nitrobenzyl group gave 3, which can exist in only two tautomeric forms depending on the solvent. Tautomerism has been studied by means of (1)H NMR spectroscopy in a variety of solvents and solvent mixtures. Tautomer structure assignments have been supported by DFT calculations of the relative energies of the tautomers. X-ray crystallography of the N-nitrobenzyl derivative has revealed that intramolecular hydrogen bonding may be responsible for stabilizing the observed tautomers. The solvent dependence of the tautomerism of 2 and 3 confers solvatochromism. Electrochemical measurements on 2 and 3 in their respective quinone forms have revealed irreversible processes, but indicate that they are both electron-deficient with a small HOMO-LUMO gap and first reduction potentials close to those of fullerene electron acceptors. 相似文献
950.
Duer MJ García F Goodman JM Hehn JP Kowenicki RA Naseri V McPartlin M Stead ML Stein R Wright DS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(4):1251-1260
The reaction of MeAlCl2 with 'PhPLi2' in THF gives [{MeAl(PPh)3Li(4).3 THF}4(mu4-Cl)]-Li+ (1). The GaIII and InIII analogues, [{MeE(PPh)3Li(4).3 THF}4(mu4-Cl)]-Li+(THF)3 (E=Ga (2), In (3)), are obtained by the in situ reactions of MeECl2 with PhPLi2 in THF. For all of the complexes, the cage anions have an unusual cubic arrangement that is similar to a zeolite, and contain large voids (ca. 17 A). The location of the Li+ counterions in 1-3 and their coordination environment appears to subtly reflect variations in packing and lattice energy. Whereas in 1 highly mobile, loosely coordinated Li+ counterions are present, 2 and 3 contain less mobile THF-solvated counterions within the cavities. X-ray crystallographic and solid-state NMR studies are reported on 1-3, together with model DFT calculations on the selectivity of halide coordination. 相似文献