Synthesis, structure, spectroscopic properties, and electrochemistry of rare earth sandwich compounds with mixed 2,3-naphthalocyaninato and octaethylporphyrinato ligands

A series of 14 heteroleptic rare earth sandwich complexes [M(III)-(nc)(oep)] (M=Y, La-Lu except Ce and Pm; nc=2,3-naphthalocyaninate; oep = octaethylporphyrinate) have been prepared by a one-pot procedure from corresponding [M(acac)3] . nH2O (acac = acetylacetonate), metal-free porphyrin H2(oep), and naphthalonitrile the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in n-octanol. The molecular structures of four of these complexes (M = Sm, Gd, Y, Lu) are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The interplanar distance decreases from 2.823 to 2.646 A along the series as a result of lanthanide contraction. The whole series of complexes have also been characterized spectroscopically. All the electronic absorptions, except the two B-bands due to nc and the oep rings, are metal-dependent, indicating that there are substantial pi-pi interactions. The hole or the unpaired electron in these double-deckers is delocalized over both macrocyclic ligands, as evidenced by the co-appearance of the IR marker bands for the nc*- (1315-1325 cm(-1)) and oep*- (1510-1531 cm(-1)) T radical ions. Three one-electron oxidation couples and up to three one-electron reduction couples have been revealed by electrochemical methods. All the potentials are linearly dependent on the size of the metal center. The changes in absorption spectra during the first electro-oxidation and reduction of the La(III), Eu(III), and Y(III) double-deckers have also been studied spectroelectrochemically. The spectral data recorded for [M(III)(nc)(oep)]-(M = Y, La-Lu except Ce and Pm) reduced chemically with hydrazine hydrate are in accord with those obtained by spectroelectrochemical methods. The first heteroleptic naphthalocyaninate-containing triple-deckers [M(III)2(nc)-(oep)2] (M = Nd, Eu) have also been prepared by a raise-by-one-story method by using [M(III)(nc)(oep)] (M = Nd, Eu), [M(acac)3] . nH2O (M = Nd, Eu), and H2(oep) as starting materials. The compounds adopt a symmetrical triple-decker structure with two outer oep rings and one inner nc ring, which has been confirmed by 'H NMR spectroscopy and X-ray structural determination of the Nd complex. Both compounds give a near-IR absorption at 1021 nm (for M=Nd) or 1101 nm (for M = Eu), which has rarely been observed for neutral (or hole-free) triple-decker complexes and can be ascribed to the lowest-energy Q'(0, 0) transition. Similarly to the double-decker analogues. these triple-decker complexes undergo a series of one-electron transfer processes with a relatively small potential gap (1.1 -1.2 V) between the first oxidation and the first reduction.

2,6-Bis(diphenylphosphino)pyridine-bridged hetero-polynuclear complexes consolidated by Fe-->M (M = Ag, Hg) dative bonding

The bridging phosphine ligand 2,6-bis(diphenylphosphino)pyridine (L) was used to synthesize a new, neutral organometallic ligand [Fe(CO)(4)](2)(micro-L) 1, which exhibits eclipsed and staggered conformations in two crystalline forms. This Fe,N,Fe-tridentate ligand reacts with silver perchlorate to form the hetero-trinuclear complex [[Fe(CO)(4)](2)Ag(micro-L)](ClO(4)) 2, in which the central silver(I) atom bridges a pair of iron(0) atoms at Fe-Ag distances of 2.627(3) and 2.652(3) A; the Fe-Ag-Fe angle is 170.98(9) degrees. The reaction of 1 with mercury(II) chloride gives [Fe(CO)(4)](2)Hg(2)Cl(4)(micro-L), 3. The ligand also reacts with mercury(II) acetate to form a hetero-octanuclear complex [[Fe(CO)(3)Hg](2)(micro-L)](2) 4 and a novel hetero-heptanuclear complex Fe(3)(CO)(8)Hg(4)(micro-L)(2)(MeCO(2))(2) 5. Complex 4 displays a square metallic core in which the iron and mercury atoms occupy the corners and the centers of the edges, respectively. The metal atoms in 5 are linked to form a kinky line with bends at the iron atoms.

New antiviral cassane furanoditerpenes from Caesalpinia minax

A bioassay-guided study led to the isolation of five new cassane furanoditerpenes, designated as caesalmin C (1), D (2), E (3), F (4), and G (5), along with stigmasterol (6) from the seeds of Caesalpinia minax. The (1)H and (13)C NMR spectra were completely assigned by using a combination of 2D NMR analyses. The structures of all five furanoditerpenes were confirmed by X-ray analyses. The structure of 6 was verified by X-ray analysis for the first time. The bioassay results showed that the anti-Para3 virus activity of tetracyclic furanoditerpenoids 1-4 is more potent than that of the furanoditerpenoid lactone 5, which is in turn better than 6. As the major components of the plant possess significant potent activity, it may be feasible to develop new antiviral agents from this source.

A novel luminescent copper(I) complex containing an acetylenediide-bridged, butterfly-shaped tetranuclear core

A novel luminescent acetylenediide-bridged tetranuclear copper(I) complex [Cu4(mu-Ph2Ppypz)4(mu 4-eta 1,eta 2-C identical to C)]-(ClO4)2 [Ph2Ppypz = 2-(diphenylphosphino-6-pyrazol-1-yl)pyridine] has been synthesized and structurally characterized by X-ray crystallography.

Rhodizonate and croconate dianions as divergent hydrogen-bond acceptors in the self-assembly of supramolecular structures

The C5O5(2-) and relatively unstable C6O6(2-) dianions, each serving as a hub for binding with a set of convergent NH donor groups of four phenylurea molecules, have been generated in situ and stabilized in nearly isostructural hydrogen-bonded host lattices.

A novel 1:1 complex of potassium mikanin-3-O-sulfate with methanol

Mikanin-3-O-sulfate (1), in the form of its potassium salt, together with mikanin (2) and alpinetin (3) were isolated from Mikania micrantha. The crystal structures of K(1) x CH3OH, 2 and 3 x H2O were established by X-ray crystallography. The potassium ions in K(1) x CHO3H are bridged by O5, O7 and O8 to form a chain of face-sharing KO8 coordination polyhedra, from which the aglycon units are outstretched to form a polymeric molecular column. Adjacent molecular columns are linked by pi-pi stacking between parallel, intercalating aglycon units to form layers matching the (101) family of planes, which are further interconnected into a three-dimensional supramolecular assembly. Sulfation at 3-OH induced better co-planarity and conjugation of the rings.

Low-valent chemistry of cobalt amide. Synthesis and structural characterization of cobalt(II) amido, aryloxide, and thiolate compounds

The binuclear cobalt(II) amide complex [(CoL2)2-(TMEDA)] (1) [L = N(Si(t)BuMe2)(2-C5H3N-6-Me); TMEDA = Me2NCH2CH2NMe2] has been synthesized by the reaction of anhydrous CoCl2 with 2 equiv of [Li(L)(TMEDA)]. X-ray crystallography revealed that complex 1 consists of two [CoL2] units linked by one TMEDA ligand molecule, which binds in an unusual N,N'-bridging mode. Protolysis of 1 with the bulky phenol Ar(Me)OH (Ar(Me) = 2,6-(t)Bu2-4-MeC6H2) and thiophenol ArSH (Ar = 2,4,6-(t)Bu3C6H2) gives the neutral monomeric cobalt(II) bis(aryloxide) [Co(OAr(Me))2(TMEDA)] (2) and dithiolate [Co(SAr)2(TMEDA)] (3), respectively. Complexes 1-3 have been characterized by mass spectrometry, microanalysis, magnetic moment, and melting-point measurements, in addition to X-ray crystallography.

Argentophilicity and solvent-induced structural diversity in double salts of silver acetylide with silver perfluoroalkyl carboxylates

A series of novel double salts of silver(I) were isolated by dissolving Ag(2)C(2) in a concentrated aqueous solution of R(F)CO(2)Ag (R(F) = CF(3), C(2)F(5)) and AgBF(4). Different ancillary solvento ligands such as H(2)O, CH(3)CN, and C(2)H(5)CN were found to affect the crystallization process that led to the assembly of various silver(I) cages with embedded C(2)(2-) ions. 2Ag(2)C(2) x 12CF(3)CO(2)Ag x 5H(2)O (1) consists of two independent C(2)@Ag(7) cages, each having the shape of a basket with a square base. Ag(2)C(2) x 6CF(3)CO(2)Ag x 3CH(3)CN (2) contains a zigzag chain of edge-sharing triangulated dodecahedra, and 4Ag(2)C(2) x 23CF(3)CO(2)Ag x 7C(2)H(5)CN x 2.5H(2)O (3) features an unusual double-walled silver column constructed from the fusion of four different kinds of irregular polyhedra. Ag(2)C(2) x 10C(2)F(5)CO(2)Ag x 9.5H(2)O (4), Ag(2)C(2) x 9C(2)F(5)CO(2)Ag x 3CH(3)CN x H(2)O (5), and Ag(2)C(2) x 6C(2)F(5)CO(2)Ag x 2C(2)H(5)CN (6) all contain an edge-sharing double cage with each single cage in the shape of a square antiprism, a capped square antiprism, and a triangulated dodecahedron, respectively.

Furanoditerpenoid lactones from the seeds of Caesalpinia minax Hance

Two furanoditerpenoid lactones, were isolated from the seeds of Caesalpinia minax Hance. Their structures and stereochemistry have been established by spectral data and single crystal X-ray analysis.

Inclusion compounds of tetrakis(4-nitrophenyl)methane: C-H...O networks, pseudopolymorphism, and structural transformations

Tetrakis(4-nitrophenyl)methane is a new host material with considerable structural adaptability over a range of solvents. The crystal structures of 14 of these solvates have been determined and classified into three groups. The diamondoid group, wherein the host molecules form a 2-fold interpenetrated diamondoid network structure, is unprecedented in that network connections are made exclusively with weak C-H...O and pi...pi interactions. This group consists of the solvates of THF, dioxane, nitrobenzene, 4-bromoanisole, anisole, phenetole, p-xylene, and chlorobenzene. The rhombohedral group, which is characterized by specific host.guest interactions of the C-H...O and halogen...O2N type, consists of the solvates of CHCl3 and CHBr3 and somewhat surprisingly DMF, which shows an unusual 3-fold disorder mimicking in part the shape and size of the haloform molecules though not their orientation. The third group comprises solvent-rich solvates of the host with mesitylene, collidine, and o-xylene with quite different crystal structures. The THF solvate was found to lose solvent over limited temperature ranges transforming reversibly from the diamondoid structure to the rhombohedral structure. A mechanism for this process is outlined. Material from which solvent has been removed by heating was also found to resolvate upon soaking in appropriate solvents. In summary, the title compound forms a host network that is partially robust and in part flexible. It is possible that this fluxional nature of the host network derives from the weakness of the connecting interactions.

Tetrapyrrole derivatives substituted with ferrocenylethynyl moieties. synthesis and electrochemical studies

Up to eight redox-active ferrocenyl units have been incorporated, through the unsaturated ethynyl linkers, on the periphery of a series of cyclic tetrapyrrole derivatives including zinc(II) phthalocyanine and 2,3-naphthalocyanine, and nickel(II) meso-diphenylporphyrin. The synthesis of the former two macrocycles 4 and 7 involves the Sonogashira coupling reaction of ferrocenylethyne with 4,5-dichlorophthalonitrile (1) or 6,7-dibromonaphthalonitrile (5), respectively, followed by a base-promoted cyclization. The meso-bis(ferrocenylethynyl)porphyrin 11 has been prepared from the dibromo analogue 10 also by a palladium-catalyzed coupling reaction. These novel macrocyclic compounds have been spectroscopically and electrochemically characterized. As revealed by cyclic voltammetry, the ferrocenyl moieties appear to be electrochemically independent in these complexes and there is no significant electronic coupling among the iron(II) centers.

Weakly coordinating nature of a carborane cage bearing different halogen atoms. Synthesis and structural characterization of icosahedral mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I)

Mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I), have been prepared by treatment of [Me3NH][1-H-CB11H5X6] (X = Cl, Br, I) with proper halogenating reagents at 180-220 degrees C in a sealed tube in high yield. These new anions are fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some are further confirmed by single-crystal X-ray analyses. The weakly coordinating nature of these anions is probed by 29Si chemical shifts of the resulting Pri3Si(1-H-CB11Y5X6) compounds. The results suggest that the coordinating ability of these anions is mainly dependent on the substituents at 7-12 positions (namely, X atoms), and the contribution from the upper belt substituents Y is relatively small. These suggestions are consistent with the results obtained from the structural study of silver salts of mixed halo- and perhalocarborane anions.

Formation of mono-, bi-, tri-, and tetranuclear Ag(I) complexes of C3-symmetric tripodal benzimidazole ligands

The C3-symmetric tripodal ligand tris(2-benzimidazolylmethyl)amine (ntb) and its alkyl-substituted derivatives tris(N-R-benzimidazol-2-ylmethyl)amine (R = methyl, Mentb; R = ethyl, Etntb; R = propyl, Prntb) react with various silver(I) salts to afford mononuclear [Ag(Prntb)(CF3SO3)].0.25H2O, 1, binuclear [Ag2(Mentb)2](CF3SO3)2.H2O, 2, trinuclear [Ag3(Etntb)2](ClO4)3.CH3OH, 3, and tetranuclear [Ag4(ntb)2(CH3CN)2(CF3CO2)2](CF3CO2)2.2H2O, 4. All four complexes have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. The Ag(I) ion in 1 is coordinated to the three imine nitrogen atoms of the Prntb ligand and one oxygen atom of the trifluoromethanesulfonate anion in a distorted tetrahedral environment. Dinuclear 2 has C2 symmetry with each Ag(I) atom trigonally coordinated by two arms of one Mentb and one arm of another. Trinuclear 3 has C3 symmetry with a Ag3 regular triangle sandwiched between a pair of Etntb ligands such that one arm of each ligand is involved in linear coordination about an Ag(I) atom. In the tetranuclear complex 4, two linearly coordinated Ag(I) atoms lying on the molecular C2 axis are bridged by a pair of ntb ligands and the remaining pendant arm of each ntb ligand is attached to another Ag(I) atom whose tetrahedral coordination sphere is completed by an acetonitrile molecule and a chelating trifluoroacetate anion. Complexes 2 and 3 may be regarded as an aggregation of two tridentate ligands by a silver dimer and a trinuclear cluster with weak Ag...Ag interactions, respectively, while in 4 the aggregation of two tripodal ligands by four Ag(I) ions affords a multicomponent internal cavity. The packing modes of complexes 1-3 are dominated by weak supramolecular pi...pi and CH...pi interactions. Hexagonal or square channels are generated in 1 and 2, and a honeycomb layer structure is formed in 3 with solvate molecules and counteranions occupying the voids. The crystal structure of 4 consists of a three-dimensional network consolidated by NH...O and OH...O hydrogen bonds.

Synthesis and structural characterization of highly chlorinated, brominated, iodinated, and methylated carborane anions, 1-H-CB9X9-, 1-NH2-CB9X9- (X = Cl, Br, I), and 1-H-CB9(CH3)9-

The highly chlorinated, brominated, and iodinated carborane anions 1-R-CB9X9- (R = H, NH2; X = Cl, Br, I) were prepared in high yields by treatment of [Me3NH][1-R-CB9H9] with excess ICl, Br2/triflic acid, and I2/triflic acid, respectively, in sealed tubes at 180-240 degrees C. With the aid of a Pd catalyst, B-I bonds could be converted into the B-Me bonds by treatment with excess MeMgBr, which led to the preparation of the permethylated species 1-H-CB9Me9- in good yield. These new anions were fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some were further characterized by single-crystal X-ray analyses. The weakly coordinating nature of these new anions was probed by 29Si chemical shifts.

Highly regioselective synthesis of 2,3,4-trisubstituted 1H-pyrroles: a formal total synthesis of lukianol A

A combined use of alpha-lithiation and nucleophilic substitutions of N,N-dimethyl 3,4-bis(trimethylsilyl)-1H-pyrrole-1-sulfonamide 8c led to several 2-substituted 3, 4-bis(trimethylsilyl)-1H-pyrrole-1-sulfonamides. Utilizing the beta-effect of a trimethylsilyl group, a highly regioselective synthesis of 2,3,4-trisubstituted 1H-pyrroles 23 and 34 was accomplished. The marine natural product lukianol A (3) was prepared utilizing this strategy.

Structure of salicylaldehyde thiosemicarbazone

C8H9N3OS, monoclinic, C2/c, a = 14.206 (3), b = 14.244 (4), c = 10.457 (4) A, beta = 116.18(2) degrees, V = 1898.9 (8) A3, Z = 8, Dm = 1.387, D chi = 1.366 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 2.90 cm-1, F(000) = 816.0, T = 298 K, final R = 0.0429 for 1322 observed reflections. The S and hydrazinic N atoms lie trans. The lowering of antibacterial activity compared to that of 4-phenylthiosemicarbazide may be correlated with the decrease in negative charge on the hydrazinic N atom. The crystal structure is stabilized by hydrogen bonding, stacking interactions and van der Waals forces.

New Oleanene-type Triterpenes from Abrus precatorius and X-ray Crystal Structure of Abrusgenic Acid-Methanol 1:1 Solvate

From ABRUS PRECATORIUS Abl. triterpenoids abruslactone, methyl abrusgenate and abrusgenic acid were isolated and elucidated by spectroscopic and X-ray techniques.

Hexamethylenetetramine Hexahydrate: A New Type of Clathrate Hydrate

Hexamethylenetetramine hexahydrate has a three-dimensional framework structure of hydrogen-bonded water molecules. Each hexamethylenetetramine molecule is located in a cavity within this framework but is linked to the water structure by hydrogen-bonds through three of its four nitrogen atoms.