Construction of triangular metallomacrocycles: [M3(1,2-bis(2,2':6',2''-terpyridin-4-yl-ethynyl)benzene)3][M = Ru(II), Fe(II), 2Ru(II)Fe(II)

Complexation of a predesigned (1,2-bis(2,2':6',2'-terpyridin-4-yl-ethynyl)benzene) ligand possessing a 60 degrees angle between two terpyridines with transition metals [Fe(II) and Ru(II)] afforded the self-assembled, triangular metallomacrocycles.     

Highly efficient retro-cycloaddition reaction of isoxazolino[4,5:1,2][60]- and -[70]fullerenes

Isoxazolino[4,5:1,2][60]- and -[70]fullerenes undergo an efficient retro-cycloaddition reaction to pristine fullerene by thermal treatment in the presence of an excess of a dienophile and Cu(II) catalysis, which can be selectively used in the presence of malonate or pyrrolidine cycloadducts. Trapping experiments using N-phenylmaleimide as dipolarophile have shown that the reaction mechanism occurs by thermal removal of the nitrile oxide 1,3-dipole, in a process which is favored by the presence of Cu(II) as the catalyst. The ESI-MS study supports the observed retro-cycloaddition process for both C60 and C70 derivatives. In contrast to previous electrochemical retro-cycloaddition processes observed in fulleropyrrolidines, isoxazolinofullerenes were stable under oxidative conditions.     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Synthesis of fullerene adducts with terpyridyl- or pyridylpyrrolidine groups in trans-1 positions

Two C(60) hexakis-adducts (2 and 3) were synthesized by using a protection-deprotection strategy. The symmetric fullerene tetrakis-adduct 8 was obtained by anthracene removal from the hexakis-adduct 7. Reaction of 8 with terpyridylglycine or pyridylglycine afforded two hexakis-adducts, 2 and 3. By using the retro-cyclopropanation reaction, the four malonate addends located on the equatorial belt of the hexakis-adducts were removed to afford two trans-1 bis-adducts, 4 and 5, with terpyridyl- or pyridylpyrrolidine groups. The structures of 2 and 3 were confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and (1)H, (13)C, and COSY NMR, and UV-visible spectroscopy. The cyclic voltammograms of fullerene multiadducts 2, 3, and 9 show irreversible reductions. Self-assembled monolayers (SAMs) of 1 and 3 were formed on gold surfaces through nitrogen adsorption. SAMs of 3 represent the first example of a fullerene hexakis-adduct formed on gold surfaces through nitrogen adsorption. Controlled potential electrolyses (CPE) were conducted to prepare trans-1 bis-adducts 4 and 5 modified with terpyridyl and pyridyl groups.     

Water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with amino acids

New water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with aliphatic amino acids (glycine, N-methylglycine, and alanine) have been prepared. Within the biological “transparency window” (700–900 nm) of their electronic absorption spectra, narrow bands of Nd³⁺ are found: ⁴F_7/2 ← ⁴I_9/2; ⁴F_5/2 ← ⁴I_9/2; ⁴F_3/2 ← ⁴I_9/2 (750, 810, and 880 nm). Such complexes can be used as markers for biological tissues visualization.     

The intramolecular rearrangement of phosphinohydrazides [R'2P-NR-NR-M] → [RN═PR'2-NR-M]: general rules and exceptions. transformations of bulky phosphinohydrazines (R-NH-N(PPh2)2, R = tBu, Ph2P)

Reactions of diphosphinohydrazines R-NH-N(PPh(2))(2) (R = tBu (1), Ph(2)P (3)) with some metalation reagents (Co[N(SiMe(3))(2)](2), LiN(SiMe(3))(2), La[N(SiMe(3))(2)](3), nBuLi, MeLi) were performed. Compound 1 was synthesized by the reaction of Ph(2)PCl with tert-butylhydrazine hydrochloride in 83% yield. This compound reveals temperature-dependent (31)P NMR spectra due to hindered rotation about the P-N bonds. Complicated redox reaction of 1 with Co[N(SiMe(3))(2)](2) proceeds with cleavage of the P-N and N-N bonds to form a binuclear cobalt complex [Co{HN(PPh(2))(2)-κ(2)P,P'}(2)(μ-PPh(2))](2) (2) demonstrating a short Co···Co distance of 2.3857(5) ?, which implies a formal double bond between the Co atoms. Strong nucleophiles (nBuLi, MeLi) cause fragmentation of the molecules 1 and 3, while reactions of 3 with lithium and lanthanum silylamides give products of the NNP → NPN rearrangement [Li{Ph(2)P(NPPh(2))(2)-κ(2)N,N'}(THF)(2)] (4) and [La{Ph(2)P(NPPh(2))(2)-κ(2)N,N'}{N(SiMe(3))(2)}(2)] (5), respectively. These complexes represent the first examples of a κ(2)N,N' bonding mode for the triphosphazenide ligand [(Ph(2)PN)(2)PPh(2)](-). DFT calculations showed large energy gain (52.1 kcal/mol) of the [NNP](-) to [NPN](-) anion rearrangement.     

Synthesis of trans-1, trans-2, trans-3, and trans-4 bisadducts of C60 by regio- and stereoselective tether-directed remote functionalization

The double Bingel reaction of fullerene C60 with bismalonates attached to a Tr?ger base derived tether afforded trans-1, trans-2, trans-3, and trans-4 bisadducts with excellent regioselectivity. In particular, enantiomerically pure bisadducts with inherently chiral trans-2 or trans-3 addition patterns were prepared starting from enantiomerically pure bismalonates. The absolute configuration of the trans-2 and trans-3 bisadducts was established from their CD spectra. The excellent diastereoselectivity in the double additions to give the trans-2 bisadducts is particularly remarkable given the large distance between the two reacting bonds in opposite hemispheres of the fullerene that is spanned by the tether. Now, all inherently chiral double addition patterns are readily available by tether-directed functionalization using appropriate chiral, nonracemic spacers.