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Treatment of an open-cage fullerene, designated as MMK-9, with (Ph3P)4Pt in toluene solution at room temperature allows a (PPh3)2Pt unit to be incorporated into the rim of the cage so that it becomes an integral part of the carbon cage skeleton. The structure of the adduct has been determined by single crystal X-ray diffraction and reveals that the platinum atom has planar PtC2P2 coordination, rather than the usual η2-bonding to an intact C–C double bond of the fullerene.

Non-luminescent, isostructural crystals of [(C6H11NC)2Au](EF6)·C6H6 (E = As, Sb) lose benzene upon standing in air to produce green luminescent (E = As) or blue luminescent (E = Sb) powders. Previous studies have shown that the two-coordinate cation, [(C6H11NC)2Au]+, self-associates to form luminescent crystals that contain linear or nearly linear chains of cations and display unusual polymorphic, vapochromic, and/or thermochromic properties. Here, we report the formation of non-luminescent crystalline salts in which individual [(C6H11NC)2Au]+ ions are isolated from one another. In [(C6H11NC)2Au](BArF24) ((BArF24)− is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) each cation is surrounded by two anions that prohibit any close approach of the gold ions. Crystallization of [(C6H11NC)2Au](EF6) (E = As or Sb, but not P) from benzene solution produces colorless, non-emissive crystals of the solvates [(C6H11NC)2Au](EF6)·C6H6. These two solvates are isostructural and contain columns in which cations and benzene molecules alternate. With the benzene molecules separating the cations, the shortest distances between gold ions are 6.936(2) Å for E = As and 6.9717(19) Å for E = Sb. Upon removal from the mother liquor, these crystals crack due to the loss of benzene from the crystal and form luminescent powders. Crystals of [(C6H11NC)2Au](SbF6)·C6H6 that powder out form a pale yellow powder with a blue luminescence with emission spectra and powder X-ray diffraction data that show that the previously characterized [(C6H11NC)2Au](SbF6) is formed. In the process, the distances between the gold(i) ions decrease to ∼3 Å and half of the cyclohexyl groups move from an axial orientation to an equatorial one. Remarkably, when crystals of [(C6H11NC)2Au](AsF6)·C6H6 stand in air, they lose benzene and are converted into the yellow, green-luminescent polymorph of [(C6H11NC)2Au](AsF6) rather than the colorless, blue-luminescent polymorph. Paradoxically, the yellow, green-luminescent powder that forms as well as authentic crystals of the yellow, green-luminescent polymorph of [(C6H11NC)2Au](AsF6) are sensitive to benzene vapor and are converted by exposure to benzene vapor into the colorless, blue-luminescent polymorph., Non-luminescent crystals of [(C6H11NC)2Au](AsF6)·C6H6 readily lose benzene to form the green-luminescent polymorph of [(C6H11NC)2Au](AsF6) rather than the blue-luminescent polymorph.

Variations in crystallization conditions produce dramatic changes in the composition and geometry of solvated porphyrin-fullerene cocrystals. The products obtained by cocrystallization from a benze...

Noncoordinating anions, which generally play a subordinate role in coordination chemistry, alter the structure, the luminescence, as well as the thermochromic and vapochromic behaviors of salts of the two-coordinate cation, [(C6H11NC)2Au]+. Thus whereas the yellow polymorphs of [(C6H11NC)2Au](PF6) and [(C6H11NC)2Au](AsF6) contain single chains of cations and are vapochromic, yellow [(C6H11NC)2Au](SbF6) does not form the same polymorph and is not vapochromic but contains two distinct chains of cations connected through aurophilic interactions. Mixed crystals such as [(C6H11NC)2Au](PF6)0.50(AsF6)0.50 have been prepared by adding diethyl ether to a dichloromethane solution containing equimolar amounts of [(C6H11NC)2Au](PF6) and [(C6H11NC)2Au](AsF6). The initial (kinetic) product for the three combinations of anions ((PF6)-/(AsF6)-, (PF6)-/(SbF6)-, and (AsF6)-/(SbF6)-) was a precipitate of fine yellow needles with a green emission, which were gradually transformed at rates that depended on the anions present into colorless crystals with a blue emission. Whereas neither polymorph of [(C6H11NC)2Au](PF6) nor [(C6H11NC)2Au](SbF6) is thermochromic, the colorless mixed crystal [(C6H11NC)2Au](PF6)0.50(SbF6)0.50 is thermochromic and converts from blue-emitting to green-emitting at 87-95 °C. The temperature required to transform a crystal of the type [(C6H11NC)2Au](PF6)n(AsF6)1-n from colorless (blue-emitting) to yellow (green-emitting) increases as the fraction of hexafluorophosphate ion in the crystal increases. The yellow crystals of [(C6H11NC)2Au](PF6)0.75(AsF6)0.25, [(C6H11NC)2Au](PF6)0.50(AsF6)0.50, and [(C6H11NC)2Au](PF6)0.25(AsF6)0.75 are vapochromic, whereas the yellow crystals of [(C6H11NC)2Au](PF6)0.50(SbF6)0.50 and [(C6H11NC)2Au](AsF6)0.50(SbF6)0.50 are not.

The synthesis of pyreno[a]pyrene-based helicene hybrids was achieved in good yield via a four-fold alkyne benzannulation reaction that was promoted by Bronsted acid. The molecules are configuration...

This investigation presents a systematic examination of the late transition metal octaethylporphyrins MII(OEP) with M = Co, Ni, Cu, and Zn as cocrystallization agents for C60. In each case, the ful...

Diastereoselective Lewis acid-mediated additions of nucleophilic alkenes to N-sulfonyl imines are reported. The canonical polar Felkin-Anh model describing additions to carbonyls does not adequately describe analogous additions to N-sulfonyl imines. Herein, we describe the development of conditions to produce both syn and anti products with high diastereoselectivity and good yields. A stereoelectronic model consistent with experimental outcomes is also proposed.

Purified samples of Ho3 N@C2 (22010)-C78 and Tb3 N@C2 (22010)-C78 have been isolated by two distinct processes from the rich array of fullerenes and endohedral fullerenes present in carbon soot from graphite rods doped with Ho2 O3 or Tb4 O7 . Crystallographic analysis of the endohedral fullerenes as cocrystals with Ni(OEP) (in which OEP is the dianion of octaethylporphyrin) shows that both molecules contain the chiral C2 (22010)-C78 cage. This cage does not obey the isolated pentagon rule (IPR) but has two sites where two pentagons share a common C-C bond. These pentalene units bind two of the metal ions, whereas the third metal resides near a hexagon of the cage. Inside the cages, the Ho3 N or Tb3 N unit is planar. Ho3 N@C2 (22010)-C78 and Tb3 N@C2 (22010)-C78 use the same cage previously found for Gd3 N@C2 (22010)-C78 rather than the IPR-obeying cage found in Sc3 N@D3h -C78 .

With aromatic and aliphatic thiol-S donor Schiff base ligands, the copper–sulfur clusters, [(L1)8CuI6CuII2](ClO4)2·DMF·0.5CH3OH (1) and [(L2)12CuI5CuII11(μ4-S)(μ4-O)6](ClO4)·4H2O, respectively, hav...

Examination of crystals of cis-Ir(CO)2X(p-toluidine) (X = Cl, Br, I), by single crystal X-ray diffraction shows that the individual monomers self-associate to form extended columns with Ir⋯Ir separations ranging from 3.33 A for the chloro complex to 3.68 A in the iodo complex. The columnar structure is reinforced by hydrogen bonding between the halide ligand in one molecule with an N-H group in an adjacent molecule. This hydrogen bonding causes adjacent molecules to adopt nearly eclipsed orientations. In contrast, the positions of the methyl groups in cis-Ir(CO)2Cl(o-toluidine) and cis-Ir(CO)2Cl(2,6-dimethylaniline) limit intermolecular interactions to the formation of dimers connected by Ir⋯Ir interactions, and hydrogen bonding again occurs between the halide ligand in one molecule and the N-H group in an adjacent molecule. The UV/vis spectrum of cis-Ir(CO)2Cl(p-toluidine) provides evidence that the self-association also occurs in solution. The positive ion mass spectrum of laser ablated crystals of cis-Ir(CO)2Br(p-toluidine) reveals the presence of monomeric, dimeric, and trimeric cations.

A titanium-based heterobimetallic single-source precursor [Y2Ti4(μ3-O)4(μ2-O)3(H2O)(TFA)8(THF)5].3(THF) (1) (where TFA = trifluoroacetato and THF = tetrahydrofuran) was successfully used to fabricate pyrochlore-structured Y2Ti2O7–2TiO2 composite thin films on fluorine-doped tin oxide (FTO) substrates using the aerosol-assisted chemical vapor deposition technique (AACVD). The precursor complex (1), isolated in crystalline form by reacting yttrium (III) acetate monohydrate with titanium (IV) isopropoxide and trifluroacetic acid in THF solution, was characterized by physicochemical methods such as melting point, microanalysis, FT-IR, 1H-NMR, thermogravimetric analyses (TGA/DTG), and single-crystal X-ray diffraction. Thin films prepared at 550 °C were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission gun-scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX) which demonstrated the development of mesoporous structured microballs of Y2Ti2O7–2TiO2 with precise stoichiometry. The optical analysis showed that Y2Ti2O7–2TiO2 has a direct optical band gap of 1.8 eV. Photo-oxidation of water via Y2Ti2O7–2TiO2 thin films was carried out under simulated solar irradiation of AM 1.5 G (100 mW cm−2) using three-electrode photoelectrochemical cell in of in three separate 0.5 M electrolyte solutions of NaOH (pH = 13.5), Na2SO4 (pH = 7.2), and citrate buffer (pH = 4). A best photocurrent density of ~ 60 μA cm−2 at + 0.8 V vs. SCE was observed at pH of 13.5. These observations were further validated by electrochemical impedance spectroscopy (EIS) studies in terms of charge transportation and its recombination time.

Two new molecular boxes, the mono-bromo box [Au6 (Triphos)4 Br](SbF6 )5 ⋅6(CH2 Cl2 ), 4 mB, and the dibromo box, [Au6 (Triphos)4 Br2 ⋅H2 O](SbF6 )4 ⋅4(CH2 Cl2 ), 5 dB, have been prepared in crystalline form. Although constructed from non-luminescent components, both are strongly luminescent. Like its chloro counterpart, the mono-bromo box [Au6 (Triphos)4 Br](SbF6 )5 ⋅6(CH2 Cl2 ), 4 mB, is mechanochromic. Under grinding, it loses its luminescence. The bromo-bridged helicate, [(μ-Br){Au3 (Triphos)2 }2 ](CF3 SO3 )5 ⋅2(CH2 Cl2 ), 3μ-H, with a cation that is isomeric with the box [Au6 (Triphos)4 Br]5+ , has also been prepared and crystallographically characterized. Unlike its chloro analogue, [(μ-Br){Au3 (Triphos)2 }2 ](CF3 SO3 )5 ⋅2(CH2 Cl2 ) is not luminescent. Thus, the cation produced upon grinding may be the cation present in the bromo-bridged helicate, [(μ-Br){Au3 (Triphos)2 }2 ](CF3 SO3 )5 ⋅2(CH2 Cl2 ), 3μ-H. The dibromo box, [Au6 (Triphos)4 Br2 ⋅H2 O](SbF6 )4 ⋅4(CH2 Cl2 ), 5 dB, is not significantly mechanochromic.

Carbon disulfide is cleaved by n-propyldiphenylphosphine and nickel(II) bromide in a one-step process, to form two unprecedented complexes: orange, [Ni(S2 C2 (Pn PrPh2 )2 )Br(Pn PrPh2 )]Br⋅CS2 (1) and purple [Ni{η2 -SC(Pn PrPh2 )2 }Br(Pn PrPh2 )]Br⋅0.5CS2 (2). Orange (1) contains a dithiolene-related ligand that results from carbon-carbon bond formation, while purple (2) contains a remarkable ligand in which two n-propyldiphenylphosphine molecules have added to a carbon atom of a CS unit that is coordinated to nickel.

The mono- and di-chloroform solvates of [Au2 (μ-1,2-bis(diphenylarsino)ethane)2 ](AsF6 )2 undergo single-crystal-to-single-crystal transformations that result in gain (over 12 hours) or slow loss (over five years) of only one chloroform molecule. The change in solvation results in changes in the structure and luminescence of the digold cation. The cation consists of a pair of slightly bent As-Au-As units that are connected through the two bridging dpae ligands and by aurophilic interactions with Au⋅⋅⋅Au contacts of 3.05152(15) A in the disolvate or 2.9570(5) A in the monosolvate.

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. Alt...

Aliphatic thiolato-S-bridged tri- and binuclear nickel(II) complexes have been synthesized and characterized as models for the Nip site of the A cluster of acetyl coenzyme A synthase (ACS)/carbon m...

A method has been developed for isolating a pure sample of Er2 C94 from the myriad of fullerenes and endohedral fullerenes that are formed in the electric arc process. Crystallographic analysis of Er2 C94 in a cocrystal formed with Ni(OEP) reveals that the molecule is the carbide Er2 C2 @D3 (85)-C92 . Crystals of Er2 C2 @D3 (85)-C92 ⋅Ni(octaethylporphyrin)⋅2 C7 H8 are isostructural with those of Sm2 @D3 (85)-C92 ⋅Ni(octaethylporphyrin)⋅2 (chlorobenzene). Comparisons are made between the four crystallographically characterized endohedrals (Er2 C2 @D3 (85)-C92 , Gd2 C2 @D3 (85)-C92 , La2 C2 @D3 (85)-C92 , and Sm2 @D3 (85)-C92 ) that utilize the chiral D3 (85)-C92 cage.

Luminescent gold(I) complexes ([Au6(Triphos)4Cl](PF6)5·2(CH3C6H5), [Au6(Triphos)4Cl](AsF6)5·8(CH3C6H5), and [Au6(Triphos)4Cl](SbF6)5·7(CH3C6H5) where Triphos = bis(2-diphenylphosphinoethyl)phenylphosphine) with a boxlike architecture have been prepared and crystallographically characterized. A chloride ion resides at the center of the box with two of the six gold(I) ions nearby. Mechanical grinding of blue luminescent crystals containing the cation, [Au6(Triphos)4Cl]5+, results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [μ-Cl{Au3(Triphos)2}2]5+. A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au3(Triphos)2](CF3SO3)3·4(CH3C6H5)·H2O, and the green-emitting bridged-helicate, [μ-Cl{Au3(Triphos)2}2](PF6)5·3CH3OH have been determined by single crystal X-ray diffraction.

The crystallization of two solvates of Au11(PPh3)7(SCN)3, 2Au11(PPh3)7(SCN)3·2C6H6·0.5EtOH (1) and Au11(PPh3)7(SCN)3·3EtOH (2), with (1) containing two independent molecules of the cluster, allows the positions of all of the ligands to finally be identified. Despite the bent nature of the thiocyanate ligands, they occupy similar sites to the ones that contain halogen ligands in Au11(PPh3)7Cl3, Au11(PPh3)7I3, and related molecules. However, the relative orientations of these thiocyanate ligands differ in the three cluster sites.

Attempts to form covalent C S bonds between fullerenes and dithiolene complexes, Ni(S2C2R2)2, lead only to the formation of the cocrystals C60·Ni(S2C2Ph2)2·0.5C7H8 and 2C70·2Ni(S2C2Ph2)2·C7H8. Both cocrystals contained pairs of Ni(S2C2Ph2)2 molecules that make offset face-to-face contact with Ni⋯Ni distances of 3.8793(5) A in the C60 crystal and 3.7529(9) and 3.7983(9) A in the C70 crystal. The fullerenes are nestled near the NiS4 portion of the Ni(S2C2Ph2)2 molecules. In 2C70·2Ni(S2C2Ph2)2·C7H8 there are two distinctly different interactions between the fullerene and the nickel complex. In one C70·Ni(S2C2Ph2)2 pair, the long axis of the fullerene is nearly parallel to the long axis of the nickel complex, while in the other pair, the long axis of the C70 cage is oriented nearly perpendicular to the long axis of the nickel complex. Thus, the immediate intimate contact between molecules such as fullerenes and flat molecules like Ni(S2C2Ph2)2 is not fixed, but can be altered by other aspects of crystal packing. The structure of a new solvated form of Ni(S2C2Ph2)2, Ni(S2C2Ph2)2·2C6H6, is also reported.

The piperazine double addition product, e{N(CH2CH2)2N}2C60, has its donor atoms positioned to bind Lewis acids in two orthogonal directions. It has been used to construct crystalline, 1-d and 2-d polymers through reactions with diiodine and the rhodium(ii) acetate dimer.

A simple exchange reaction between [AriPr4Sn(μ-Cl)]2 (1) and sodium azide afforded the doubly bridged Sn(II) azide, [AriPr4Sn(μ-N3)]2 (2) (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) in 85% yield. Photolysis of a diethyl ether solution of 2 for ca. 16 h yielded an azepinyl-substituted insertion product, [C6H3-2-(C6H3-2,6-iPr2)-6-(C6H3N-3,7-iPr2)Sn]2 (3). The reaction of the Lewis acid, B(C6F5)3 (BCF), or the Lewis base, pyridine, with 2 dissociates the dimer to afford the corresponding complexed monomeric Sn(II) azide, AriPr4SnN3BCF (4) in which BCF coordinates the α-nitrogen, or AriPr4Sn(pyridine)N3 (6) in which pyridine coordinates to the tin atom. Photolysis of 4 in diethyl ether for 12 h results in the insertion of the α-nitrogen of the azide group into one of the B-C bonds of the BCF acceptor to yield the tin(II) amide, AriPr4SnN(C6F5)B(C6F5)2 (5). In contrast, photolysis of 6 for over 36 h afforded no apparent reaction. A highly reactive Sn nitride intermediate, AriPr4Sn≡N, is proposed as part of the mechanistic pathway for the formation of 3 and 5 as a result of trapping the tin-centered radical isomers. This was effected by immediate freezing the samples of 2 or 4 after ca. 30 min of UV photolysis and recording their electron paramagnetic resonance spectra. These exhibited a rhombic g tensor of [g1, g2, g3] = [2.029, 1.978, 1.933]. This radical intermediate could be related to the valence isomers of the nitride [-SnIV≡N] intermediate, in isomeric equilibrium with the nitrene [-SnII-N] and nitridyl [-SnIII═N·] forms, but with the spin density on the nitrogen being quenched, possibly by the H atom abstraction to form an S = 1/2 species of formula -Sn·═N(H).

The structures of Er3N@Ih-C80 and Ho3N@Ih-C80 have been determined by single crystal X-ray diffraction in the cocrystals Er3N@Ih-C80·Ni(OEP)·2benzene and Ho3N@Ih-C80·Ni(OEP)·2benzene where OEP is the dianion of octaethylporphyrin. Comparison of the structural data for M3N@Ih-C80.with M = Gd, Tb, Dy, Ho, Er, Tm, and Sc reveals that, as the ionic radii of the metal ions increase, the anisotropic thermal ellipsoid of the nitrogen becomes more and more elongated until it is better to refine it as split and isotropic as in the cases of Gd3N@Ih-C80 and Tb3N@Ih-C80. The data also indicate that the M3N unit becomes pyramidalized to some extent when the sum of the Shannon-Prewitt crystal radii for six-coordinate M3+ of the three metal ions involved exceeds 3.05 A. There is a gradual progression in the degree of distortion as the metal ion sizes increase. This statement holds true for both homometallic and heterometallic endohedrals of the type M3N@Ih-C80.

A totally unanticipated regio- and stereoisomerically pure C2h -symmetric trans-1-(bis-pyrrolidine)-tetra-malonate hexa-adduct of C60 was obtained via a topologically controlled method, followed by a 1,3-dipolar cycloaddition reaction. The structures of the products were elucidated by 1 H and 13 C NMR and by X-ray crystallography. The unexpected regio- and stereoselectivity observed, supported by theoretical calculations, was found to be a consequence of malonate-pyrrolidine interactions.

The crystal structure determination based on 90 K data of the title imine ligand, C18H10ClNO, revealed non-merohedral twinning with three twin domains. In our experience, this is an indication of an ordering phase transition. Consequently, the structure was redetermined with higher temperature data, and a reversible phase transition was discovered. The higher temperature phase is indeed an ordered structure. At the higher temperature, the 4-chlorophenyl group has rotated by ca 7° into a crystallographic mirror plane. Warming the crystal from 90 K to 250 K changes the space group from triclinic P-1, to monoclinic P21/m. Diverse non-classical interactions are present in the crystal packing, and these are described for the phase change reported in this work. The crystal structure of the title imine ligand, measured at 100 K, has been reported on previously [Kovach et al. (2011). J. Mol. Struct. 992, 33–38].

The structure of Ni(Hpydc)2·3H2O (H2pydc = pyridine-2,6-dicarboxylic acid, also known as dipicolinic acid) has been reinvestigated at variable temperatures. At room temperature, it matches the known structure in the space groupP21/c, but at 180 K it undergoes a phase transformation to a twinned structure inCc. By 120 K, the structure is ordered and twinned withZ′ = 4, and shows interesting short hydrogen-bonding interactions that include the formation of hydroxonium species.

The unsymmetrical coordination of gold(I) by 2,2'-bipyridine (bipy) in some planar, three-coordinate cations has been examined by crystallographic and computational studies. The salts [(Ph3P)Au(bipy)]XF6 (X = P, As, Sb) form an isomorphic series in which the differences in Au-N distances range from 0.241(2) to 0.146(2) A. A second polymorph of [(Ph3P)Au(bipy)]AsF6 has also been found. Both polymorphs exhibit similar structures. The salts [(Et3P)Au(bipy)]XF6 (X = P, As, Sb) form a second isostructural series. In this series the unsymmetrical coordination of the bipy ligand is maintained, but the gold ions are disordered over two unequally populated positions that produce very similar overall structures for the cations. Although many planar, three-coordinate gold(I) complexes are strongly luminescent, the salts [(R3P)Au(bipy)]XF6 (R = Ph or Et; X = P, As, Sb) are not luminescent as solids or in solution. Computational studies revealed that a fully symmetrical structure for [(Et3P)Au(bipy)]+ is 7 kJ/mol higher in energy than the observed unsymmetrical structure and is best described as a transition state between the two limiting unsymmetrical geometries. The Au-N bonding has been examined by natural resonance theory (NRT) calculations using the "12 electron rule". The dominant Lewis structure is one with five lone pairs on Au and one bond to the P atom, which results in a saturated (12 electron) gold center and thereby inhibits the formation of any classical, 2 e- bonds between the gold and either of the bipy nitrogen atoms. The nitrogen atoms may instead donate a lone pair into an empty Au-P antibonding orbital, resulting in a three-center, four-electron (3c/4e) P-Au-N bond. The binuclear complex, [μ2-bipy(AuPPh3)2](PF6)2, has also been prepared and shown to have an aurophillic interaction between the two gold ions, which are separated by 3.0747(3) A. Despite the aurophillic interaction, this binuclear complex is not luminescent.

The averages (average deviations from the mean are given in square brackets) of uncorrected Cl—O bond distances in a perchlorate anion from an X-ray diffraction analysis of (N-{2-[bis(pyridin-2-ylmethyl)amino]ethyl}pyridine-2-carboxamidato)(nitric oxide)manganese perchlorate acetonitrile disolvate, [Mn(C20H20N5O)(NO)]ClO4·2CH3CN or [Mn(PaPy3)(NO)]ClO4·2CH3CN, decrease from 1.447 [4] Å at 10 K to 1.428 [4] Å at 170 K. The 10 K value is close to the neutron value (1.441 [1] Å) at 18 K. Comparisons are made with a second X-ray study at 30 K [1.444 (8) Å] and to libration-corrected, density functional theory (DFT), and Cambridge Structural Database (CSD) values.

According to the well-accepted mechanism, methyl-coenzyme M reductase (MCR) involves Ni-mediated thiolate-to-disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni-ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of NiII complexes comprising a tridentate N2 S donor thiol and its analogous N4 S2 donor disulfide ligands. These complexes demonstrate reversible NiII -thiolate/NiII -disulfide (both bound and unbound disulfide-S to NiII ) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.

Additions of adamantylidene (Ad) to M3 N@Ih -C80 (M=Sc, Lu) and Sc3 N@D5h -C80 have been accomplished by photochemical reactions with 2-adamantyl-2,3'-[3H]-diazirine (1). In M3 N@Ih -C80 , the addition led to rupture of the [6,6]- or [5,6]-bonds of the Ih -C80 cage, forming the [6,6]-open fulleroid as the major isomer and the [5,6]-open fulleroid as the minor isomer. In Sc3 N@D5h -C80 , the addition also proceeded regioselectively to yield three major isomeric Ad mono-adducts, despite the fact that there are nine types of C-C bonds in the D5h -C80 cage. The molecular structures of the seven Ad mono-adducts, including the positions of the encaged trimetallic nitride clusters, have been unambiguously determined through single-crystal XRD analyses. Furthermore, results have shown that stepwise addition of Ad to Lu3 N@Ih -C80 affords several Ad bis-adducts, two of which have been isolated and characterized. The X-ray structure of one bis-adduct clearly revealed that the second Ad addition took place at a [6,6]-bond close to an endohedral metal atom. Theoretical calculations have also been performed to rationalize the regioselectivity.

Conditions for the crystallization and interconversion of the green and brown polymorphs of bis(3-ethylamino-1-phenyl-but-2-en-1-ono)nickel(II) (Ni(B–Et)2), which contain planar and tetrahedral complexes in accord with previous magnetic and spectroscopic studies, have been determined. Additionally, the series of β-diketoamine-containing complexes, M(B–Et)2 and M(B–Bn)2, (M = CoII, NiII, CuII, ZnII) obtained from condensation of benzoylacetone (B) with either ethylamine (Et) or benzylamine (Bn) followed by treatment with [MCl4]2− under basic conditions has been prepared and their structures characterized crystallographically. In contrast to Ni(B–Et)2, Ni(B–Bn)2 has been crystallized only in the planar form. M(B–Et)2 and M(B–Bn)2 (M = Co or Zn) have similar, nearly tetrahedral structures, while Cu(B–Et)2 and Cu(B–Bn)2 have structures that are decidedly intermediate between tetrahedral and planar. Despite the abilities of these complexes to exist in tetrahedral, planar, or intermediate structures in solution, it has not been possible to induce much structural variation in crystalline forms. While two polymorphs of Zn(B–Bn)2 have been obtained, both have similar, tetrahedral structures. Only Ni(B–Et)2 crystallizes in both planar and tetrahedral forms. None of the complexes formed cocrystals with fullerenes or solvates in which structural variation as seen in Ni(B–Et)2 occurred.

The reaction of the piperazine mono-adduct, N(CH2CH2)2NC60, with diiodine produced well ordered, black crystals of (I2N(CH2CH2)2NI2)C60·2.884(C6H6)·0.116I2, which contains two nearly linear N-I-I units. Reaction of N(CH2CH2)2NC60 with iodine monochloride produced two materials: the dihalogen adduct, (ClIN(CH2CH2)2NICl)C60·2.3(CS2)·0.7(CH2Cl2), when crystallization occurred rapidly from carbon disulfide/dichloromethane solution or the salt, [(N(CH2CH2)2NH)C60+][ICl2-]·CS2, when crystallization happened more slowly from toluene/dichloromethane solution where hydrolysis of the iodine monochloride by adventitious water presumably occurred.

Fully spin delocalized mixed valence copper–sulfur clusters, 1 and 2, supported by μ4-sulfido and NSthiol donor ligands are synthesized and characterized. Wheel shaped 1 consists of Cu2S2 units. The unprecedented nanoball 2 can be described as S@Cu4(tetrahedron)@O6(octahedron)@Cu12S12(cage) consisting of both Cu2S2 and (μ4-S)Cu4 units. The Cu2S2 and (μ4-S)Cu4 units resemble biological CuA and CuZ sites respectively.

The photochemical reaction of piperazine with C70 produces a mono-adduct (N(CH2 CH2 )2 NC70 ) in high yield (67 %) along with three bis-adducts. These piperazine adducts can combine with various Lewis acids to form crystalline supramolecular aggregates suitable for X-ray diffraction. The structure of the mono-adduct was determined from examination of the adduct I2 N(CH2 CH2 )2 NI2 C70 that was formed by reaction of N(CH2 CH2 )2 NC70 with I2 . Crystals of polymeric {Rh2 (O2 CCF3 )4 N(CH2 CH2 )2 NC70 }n ⋅nC6 H6 that formed from reaction of the mono-adduct with Rh2 (O2 CCF3 )4 contain a sinusoidal strand of alternating molecules of N(CH2 CH2 )2 NC70 and Rh2 (O2 CCF3 )4 connected through Rh-N bonds. Silver nitrate reacts with N(CH2 CH2 )2 NC70 to form black crystals of {(Ag(NO3 ))4 (N(CH2 CH2 )2 NC70 )4 }n ⋅7nCH2 Cl2 that contain parallel, nearly linear chains of alternating (N(CH2 CH2 )2 NC70 molecules and silver ions. Four of these {Ag(NO3 )N(CH2 CH2 )2 NC70 }n chains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non-polar C70 cages encircling that core. Of the three bis-adducts, one was definitively identified through crystallization in the presence of I2 as 12 {N(CH2 CH2 )2 N}2 C70 with addends on opposite poles of the C70 cage and a structure with C2v symmetry. In 12 {I2 N(CH2 CH2 )2 N}2 C70 , individual 12 {I2 N(CH2 CH2 )2 N}2 C70 units are further connected by secondary I2⋅⋅⋅N2 interactions to form chains that occur in layers within the crystal. Halogen bond formation between a Lewis base such as a tertiary amine and I2 is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize.

The crystal structures of the title compounds, C19H19NO and C31H34N2O, were determined as part of an experiment in an undergraduate teaching laboratory that demonstrates the relationship between molecular structure and function. 1′,3′,3′-Trimethylspiro[chromene-2,2′-indoline] is both a photoswitch and thermochromic molecule. Students synthesized it and a bis-indoline adduct and compared the crystallographically determined structures to computed gas-phase models.

We report that Ce@C2v(9)-C82 forms a centrosymmetric dimer when co-crystallized with Ni(OEP) (OEP = octaethylporphyrin dianion). The crystal structure of {Ce@C2v(9)-C82}2⋅2[Ni(OEP)]⋅4 C6H6 shows that a new C−C bond with a bond length of 1.605(5) A connects the two cages. The high spin density of the singly occupied molecular orbital (SOMO) on the cage and the pyramidalization of the cage are factors that favor dimerization. In contrast, the treatment of Ni(OEP) with M@C2v(9)-C82 (M = La, Sc, and Y) results in crystallization of monomeric endohedral fullerenes. A systematic comparison of the X-ray structures of M@C2v(9)-C82 (M = Sc, Y, La, Ce, Gd, Yb, and Sm) reveals that the major metal site in each case is located at an off-center position adjacent to a hexagonal ring along the C2 axis of the C2v(9)-C82 cage. DFT calculations at the M06-2X level revealed that the positions of the metal centers in these metallofullerenes M@C2v(9)-C82 (M = Sc, Y, and Ce), as determined by single-crystal X-ray structure studies, correspond to an energy minimum for each compound.

A non-isolated pentagon rule metallic carbide clusterfullerene containing a heptagonal ring, Sc2C2@Cs(hept)-C88, was isolated from the raw soot obtained by electric arc vaporization of graphite rods packed with Sc2O3 and graphite powder under a helium atmosphere. The Sc2C2@Cs(hept)-C88 was purified by multistage high-performance liquid chromatography (HPLC), cocrystallized with Ni–(octaethylporphyrin), and characterized by single-crystal X-ray diffraction. The diffraction data revealed a zigzag Sc2C2 unit inside an unprecedented Cs(hept)-C88 carbon cage containing 13 pentagons, 32 hexagons, and 1 heptagon. Calculations suggest that the observed nonclassical fullerene could be a kinetically trapped species derived from the recently reported Sc2C2@C2v(9)-C86 via a direct C2 insertion.

The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements.

The structure of Sc3N@D 3h -C78, which has been examined crystallographically and found to obey the isolated pentagon rule (IPR), will be discussed and compared to other related endohedral fullerenes. The effect of the composition of the interior M3N unit in this and other endohedral fullerenes will be shown to influence cage structure, sometimes in a predictable fashion. Structural studies of other fullerenes will also be presented.

After more than 50 years, the synthesis and electronic structure of the first and only reported "U0 complex" [U(bipy)4 ] (1) has been reinvestigated. Additionally, its one-electron reduced product [Na(THF)6 ][U(bipy)4 ] (2) has been newly discovered. High resolution crystallographic analyses combined with magnetic and computational data show that 1 and its derivative 2 are best described as highly reduced species containing mid-to-high-valent uranium ligated by redox non-innocent ligands.

The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H2L (1). Characterization of the ligand was performed by FT-IR, 1H NMR, 13C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO3)2·6H2O and CuCl2·2H2O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.

Two related nickel(II) porphyrins, etioporphyrin-I (Etio-I) and octaethylporphyrin (OEP), were cocrystallized with C70 to produce the new cocrystal structures C70·Ni(Etio-I)·2C6H6 and C70·Ni(OEP)·2C6H6. Etio-I is a variant of OEP, where four alternating ethyl groups from OEP are replaced with methyl substituents. This isomer of etioporphyrin has the potential to act as an agent in chiral sorting of asymmetric fullerenes. However, the replacement of four ethyl groups has nontrivial structural consequences. Further host–guest investigation of M(Etio-I) (M = Co, Ni, Cu, Zn) with C60 or C70 was conducted, producing new X-ray structures of Co(Etio-I) and Zn(Etio-I), and a redetermination of Ni(Etio-I). Despite numerous and varied attempts, C60 cocrystallized with M(Etio-I) could not be obtained.

One new 2D coordination polymer of Ni(II) namely [Ni2(ndc)2(DMSO)4(H2O)] n , where ndc = naphthalene-1,4-dicarboxylic acid and DMSO = dimethyl sulfoxide, has been synthesized and characterized by elemental analysis, spectral (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. This coordination polymer possesses a 2D layer structure constructed from dinuclear nickel(II) building blocks in which two crystallographically independent Ni2+ ions are bridged by ndc2− ligands and water molecule. The ndc2− ligands adopt μ3 bridging modes, linking the metal centers into a two-dimensional coordination network. The two independent NiII cations are surrounded by dimethyl sulfoxide and naphthalene-1,4-dicarboxylate molecules in a distorted octahedron geometry. In the crystal structures of Ni(II) coordination polymer, there are non-classical hydrogen bonding arrangements and C–H∙∙∙π stacking interactions. Electrochemical behavior of [Ni2(ndc)2(DMSO)4(H2O)] n , (Ni-NDA) on the surface of carbon nanotubes (CNTs)/glassy carbon electrode (GCE) was described. The surface structure of the sensor was characterized by scanning electron microscopy (SEM). Oxidation of fructose on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS) and the results showed that the Ni-NDA/CNTs film displays excellent electrochemical catalytic activities toward fructose oxidation.

Bis-silylated and bis-germylated derivatives of Lu3 N@Ih -C80 (3, 4, 5) were successfully synthesized by the photochemical addition of disiliranes 1 a, 1 b or digermirane 2, and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron-donor properties and lower steric hindrance around the Ge-Ge bond. The 1,4-adduct structures of 3, 4, 5 were unequivocally established by single-crystal X-ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4-adducts are remarkably smaller than those of Lu3 N@Ih -C80 , because the electron-donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron-donating than the silyl groups on the basis of the redox properties and the HOMO-LUMO energies of 4 and 5. Bis-silylation and bis-germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes.

While several nonchromatographic methods are available for the isolation and purification of endohedral fullerenes of the type M3N@Ih-C80, little work has been done that would allow other members of the M3N@C2n family to be isolated with minimal chromatography. Here, we report that Gd3N@D2(35)-C88 can be isolated from the multitude of endohedral and empty cage fullerenes present in carbon soot obtained by electric-arc synthesis using Gd2O3-doped graphite rods. The procedure developed utilizes successive precipitation with the Lewis acids CaCl2 and ZnCl2 followed by treatment with amino-functionalized silica gel. The structure of the product was identified by single-crystal X-ray diffraction.

The synthesis, isolation, and characterization of a new endohedral fullerene, Sc2C88, is reported. Characterization by single crystal X-ray diffraction revealed that it is the carbide Sc2C2@C(2v)(9)-C86 with a planar, twisted Sc2C2 unit inside a previously unseen C(2v)(9)-C86 fullerene cage.