Single-Crystal X-ray Diffraction Studies of Solvated Crystals of C60 Reveal the Intermolecular Interactions between the Component Molecules.

The solid-state structures of seven solvates of C60 (C60·4tetrachloroethylene, C60·2tetrachloroethylene, C60·3benzene, C60· n-pentane, C60·diethyl ether, C60·chlorobenzene, and C60·benzene·dichloromethane) were determined by single-crystal X-ray diffraction at low temperature. At 90 K, the fullerene and solvate components are generally well-ordered and do not show the orientational disorder that plagues similar structures determined at room temperature. Interactions between the solvate molecules and the fullerene and between adjacent C60 molecules were examined and analyzed. Van der Waals and weak charge-transfer interactions are important to help to organize the individual components in these structures. The weak Lewis acid behavior of C60, such as when it cocrystallizes with diethyl ether or chlorinated solvents, is apparent. In addition, π-stacking interactions are prevalent. The solvates of C60 reported here were frequently obtained from attempts to cocrystallize C60 with another chemical compound. Although the desired cocrystals were never formed, the unincorporated molecules influenced solvate formation.

Copper coordinated ligand thioether-S and NO2(-) oxidation: relevance to the CuM site of hydroxylases.

In order to gain insight into the coordination site and oxidative activity of the CuM site of hydroxylases such as peptidylglycine α-hydroxylating monooxygenase (PHM), dopamine ß-monooxygenase (DßM), and tyramine ß-monooxygenase (TßM), we have synthesized, characterized and studied the oxidation chemistry of copper complexes chelated by tridentate N2Sthioether, N2Osulfoxide or N2Osulfone donor sets. The ligands are those of N-2-methylthiophenyl-2'-pyridinecarboxamide (HL1), and the oxidized variants, N-2-methylsulfenatophenyl-2'-pyridinecarboxamide (HL1(SO)), and N-2-methylsulfinatophenyl-2'-pyridinecarboxamide (HL1(SO2)). Our studies afforded the complexes [(L1)Cu(II)(H2O)](ClO4)·H2O (1·H2O), {[(L1(SO))Cu(II)(CH3CN)](ClO4)}n (2), [(L1)Cu(II)(ONO)] (3), [(L1(SO))Cu(II)(ONO)]n (4), [(L1)Cu(II)(NO3)]n (5), [(L1(SO))Cu(II)(NO3)]n (6) and [(L1(SO2))Cu(II)(NO3)] (7). Complexes 1 and 3 were described in a previous publication (Inorg. Chem., 2013, 52, 11084). The X-ray crystal structures revealed either distorted octahedral (in 2, 4-6) or square-pyramidal (in 1, 3) coordination geometry around Cu(II) ions of the complexes. In the presence of H2O2, conversion of 1→2, 3-5→6 and 6→7 occurs quantitatively via oxidation of thioether-S and/or Cu(ii) coordinated NO2(-) ions. Thioether-S oxidation of L1 also occurs when [L1](-) is reacted with [Cu(I)(CH3CN)4](ClO4) in DMF under O2, albeit low in yield (20%). Oxidations of thioether-S and NO2(-) were monitored by UV-Vis spectroscopy. Recovery of the sulfur oxidized ligands from their metal complexes allowed for their characterization by elemental analysis, (1)H NMR, FTIR and mass spectrometry.

Preparation and crystallographic characterization of C60{η1-Ru(CO)2(η5-C5H5)}2: a locally crowded organometallic fullerene without the usual η2-bonding.

The reaction of {(η(5)-C5H5)Ru(CO)2}2 with C60 in toluene solution under thermal or photolytic conditions produces C60{η(1)-Ru(CO)2(η(5)-C5H5)}2, whose structure has been determined by single crystal X-ray diffraction. The two Ru(CO)2(η(5)-C5H5) units are bound at the opposite ends of a hexagon on the fullerene surface and are closely intertwined.

A missing link in the transformation from asymmetric to symmetric metallofullerene cages implies a top-down fullerene formation mechanism.

Although fullerenes were discovered nearly three decades ago, the mechanism of their formation remains a mystery. Many versions of the classic 'bottom-up' formation mechanism have been advanced, starting with C2 units that build up to form chains and rings of carbon atoms and ultimately form those well-known isolated fullerenes (for example, I(h)-C60). In recent years, evidence from laboratory and interstellar observations has emerged to suggest a 'top-down' mechanism, whereby small isolated fullerenes are formed via shrinkage of giant fullerenes generated from graphene sheets. Here, we present molecular structural evidence for this top-down mechanism based on metal carbide metallofullerenes M2C2@C1(51383)-C84 (M = Y, Gd). We propose that the unique asymmetric C1(51383)-C84 cage with destabilizing fused pentagons is a preserved 'missing link' in the top-down mechanism, and in well-established rearrangement steps can form many well-known, high-symmetry fullerene structures that account for the majority of solvent-extractable metallofullerenes.

Copper complexes relevant to the catalytic cycle of copper nitrite reductase: electrochemical detection of NO(g) evolution and flipping of NO2 binding mode upon Cu(II) → Cu(I) reduction.

Copper complexes of the deprotonated tridentate ligand, N-2-methylthiophenyl-2'-pyridinecarboxamide (HL1), were synthesized and characterized as part of our investigation into the reduction of copper(II) o-nitrito complexes into the related copper nitric oxide complexes and subsequent evolution of NO(g) such as occurs in the enzyme copper nitrite reductase. Our studies afforded the complexes [(L1)Cu(II)Cl]n (1), [(L1)Cu(II)(ONO)] (2), [(L1)Cu(II)(H2O)](ClO4)·H2O (3·H2O), [(L1)Cu(II)(CH3OH)](ClO4) (4), [(L1)Cu(II)(CH3CO2)]·H2O (5·H2O), and [Co(Cp)2][(L1)Cu(I)(NO2)(CH3CN)] (6). X-ray crystal structure determinations revealed distorted square-pyramidal coordination geometry around Cu(II) ion in 1-5. Substitution of the H2O of 3 by nitrite quantitatively forms 2, featuring the κ(2)-O,O binding mode of NO2(-) to Cu(II). Reduction of 2 generates two Cu(I) species, one with κ(1)-O and other with the κ(1)-N bonded NO2(-) group. The Cu(I) analogue of 2, compound 6, was synthesized. The FTIR spectrum of 6 reveals the presence of κ(1)-N bonded NO2(-). Constant potential electrolysis corresponding to Cu(II) → Cu(I) reduction of a CH3CN solution of 2 followed by reaction with acids, CH3CO2H or HClO4 generates 5 or 3, and NO(g), identified electrochemically. The isolated Cu(I) complex 6 independently evolves one equivalent of NO(g) upon reaction with acids. Production of NO(g) was confirmed by forming [Co(TPP)NO] in CH2Cl2 (λ(max) in CH2Cl2: 414 and 536 nm, ν(NO) = 1693 cm(-1)).

Reshaping molecules through cocrystallization. Comparison of the structures of Hg{Co(CO)4}2 and Hg{Co(CO)4}2·C60·toluene.

Cocrystallization of Hg{Co(CO)4}2 with C60 produces Hg{Co(CO)4}2·C60·toluene in which the geometry of the Hg{Co(CO)4}2 molecule is rearranged to fit between the remarkably well ordered fullerenes.

High yield synthesis of a new fullerene linker and its use in the formation of a linear coordination polymer by silver complexation.

A new hexakis-fullerene adduct with two 4,5-diazafluorene groups strategically located at trans-1 positions to allow linear polymerization was selectively synthesized in very high yield. By reaction with Ag(triflate), a one dimensional metal-organic coordination polymer was obtained.

Azide addition to an endohedral metallofullerene: formation of azafulleroids of Sc3N@I(h)-C80.

The reaction of an organic azide with an endohedral metallofullerene has been investigated for the first time. Isomeric [5,6]- and [6,6]-azafulleroids can be obtained from the thermal reaction of Sc(3)N@I(h)-C(80) with 4-isopropoxyphenyl azide, while photoirradiation leads exclusively to the [6,6]-azafulleroid. An unprecedented thermal interconversion between the two isomeric azafulleroids has also been discovered.