Heteroleptic Lanthanide Complexes with Aryloxide Ligands. Synthesis and Structural Characterization of Divalent and Trivalent Samarium Aryloxide/Halide and Aryloxide/Cyclopentadienide Complexes

Synthesis of a new class of heteroleptic samarium aryloxide complexes has been achieved by the use of homoleptic samarium(II) bis(aryloxide) Sm(OAr)(2)(THF)(3) (1, Ar = C(6)H(2)Bu(t)(2)-2,6-Me-4) as a starting material, which is easily obtained by reaction of Sm(N(SiMe(3))(2))(2)(THF)(2) with 2 equiv of ArOH in THF. 1 reacts with 1 equiv of SmI(2) in THF to give Sm(II) mixed aryloxide/iodide [(ArO)Sm(&mgr;-I)(THF)(3)](2) (2), which adopts a dimeric structure via very weak Sm.I (3.534(2) ?) interactions. Reaction of 2 with C(5)Me(5)K in THF/HMPA affords the corresponding Sm(II) aryloxide/cyclopentadienide (C(5)Me(5))Sm(OAr)(HMPA)(2) (3). Oxidation of 1 with 0.5 equiv of I(2) in THF gives monomeric samarium(III) aryloxide/iodide (ArO)(2)SmI(THF)(2) (4), while the similar reaction of 1 with ClCH(2)CH(2)Cl or (t)BuCl in THF affords dimeric samarium(III) aryloxide/chloride [(ArO)(2)Sm(&mgr;-Cl)(THF)](2) (5). Crystal data for 1: monoclinic, space group P2(1), a = 9.903(3) ?, b = 16.718(5) ?, c = 13.267(2) ?, beta = 95.17(2) degrees, V = 2187(2) ?(3), Z = 2, D(c) = 1.223 g cm(-)(3), R = 0.0634. Crystal data for 2.2THF: monoclinic, space group P2(1)/a, a = 18.330(6) ?, b = 14.320(4) ?, c = 13.949(3) ?, beta = 103.16(2) degrees, V = 3563(2) ?(3), Z = 2, D(c) = 1.46 g cm(-)(3), R = 0.0606. Crystal data for 3: triclinic, space group P&onemacr;, a = 10.528(1) ?, b = 12.335(2) ?, c = 19.260(2) ?, alpha = 101.33(1) degrees, beta = 95.230(9) degrees, gamma = 108.54(1) degrees, V = 2293.1(5) ?(3), Z = 2, D(c) = 1.25 g cm(-)(3), R = 0.0358. Crystal data for 4: monoclinic, space group C2/c, a = 17.191(7) ?, b = 10.737(6) ?, c = 21.773(7) ?, beta = 98.80(3) degrees, V = 3971(3) ?(3), Z = 4, D(c) = 1.44 g cm(-)(3), R = 0.0467. Crystal data for 5: monoclinic, space group P2(1)/n, a = 13.750(3) ?, b = 17.231(3) ?, c = 14.973(6) ?, beta = 95.81(2) degrees, V = 3529(2) ?(3), Z = 2, D(c) = 1.31 g cm(-)(3), R = 0.0557.     

Synthesis in the diazasteroid group. XII Syntheses of the 10,17-diazasteroid and 10-aza-17-thiasteroid systems

Upon desulfurization with Raney Ni, the condensed heterocycles 2a,b prepared by cyclization from β-ketosulfoxides 1a,b gave β-ketones 3a,b , which were condensed with 2-carbethoxymethyl-piperidine 4 to afford the 10,17-diazasteroid 6 and the 10-aza-17-thiasteroid 7 , respectively.     

An efficient synthesis of conjugation-expanded carba- and azuliporphyrins using a bicyclo[2.2.2]octadiene-fused tripyrrane

A bicyclo[2.2.2]octadiene-fused tripyrrane was synthesized as a first versatile reagent for the preparation of π-expanded heteroporphyrins. The reaction of the tripyrrane with 1,3-diformylindene and azulene-1,3-dicarbaldehyde afforded the corresponding heteroporphyrins, which were easily converted into tetrabenzocarbaporphyrin and tribenzoazuliporphyrin by retro Diels-Alder reaction.     

Changes in surface stress of gold electrode during underpotential deposition of copper

The changes in surface stress of the evaporated gold electrode (mainly oriented to the (111) plane) during underpotential deposition (UPD) of copper in 0.1 M sulfuric acid medium or 0.1 M perchloric acid medium with and without sulfate or chloride were measured using a bending beam method. The surface stress maximum of gold electrode appeared during Cu-UPD. The co-adsorption of (bi)sulfate or chloride ions with copper atoms induced the compressive surface stress to promote the Cu-UPD. The factors influencing the surface stress or surface elastic strain were discussed in relation to the Cu-UPD structure. Dedicated to Professor Su-Il Pyun on the occasion of his 65th birthday.     

Structure and photophysical properties of porphyrin-modified metal nanoclusters with different chain lengths

Three-dimensional porphyrin-monolayer-protected gold clusters with different chain lengths (MPCs) have been prepared to examine the structure and photophysical properties, in comparison with self-assembled monolayers (SAMs) of the porphyrins on a flat gold surface. The three-dimensional porphyrin MPCs exhibit electrochemical and photophysical properties that are much closer to those of a porphyrin reference compound in solution than those of two-dimensional porphyrin SAMs on the flat gold surface. The three-dimensional architectures of porphyrin MPCs with large surface area have improved the light-harvesting efficiency relative to the corresponding porphyrin SAM on the two-dimensional flat gold surface. Time-resolved single photon counting fluorescence and transient absorption spectroscopic studies have demonstrated that undesirable quenching of the porphyrin excited singlet state via energy transfer to the gold surface of the three-dimensional MPCs is much suppressed, as compared to the quenching of the porphyrin SAMs on the two-dimensional flat gold surface. Both the quenching rate constants of the porphyrin excited singlet state by the surfaces of bulk gold and gold nanoclusters reveal weak chain length dependence of the energy transfer quenching.     

Synthesis in the diazasteroid group. V. Synthesis of the 9,14-diazasteroid system

By the condensation reaction of 2-chloroquinoline (X) and ethyl 2-pyrrolidineacetate (II), 2-[1′-(2′-carboethoxymethyl)pyrrolidyl]quinoline (XI) was prepared. Compound XI was converted to the quarternary base (XIII) having a 9,14-diazasteroid skeleton by the reduction of the ester to the corresponding alcohol followed by the quaternarization via tosylation. Compound XIII was reduced with sodium borohydride to 9,14-diazagona-1,3,5(10)-triene (III), which is suggested to have the trans-anti-trans conformation.     

Syntheses, structures, and properties of intercalation compounds of silver(I) complex with [2.2]paracyclophane

Reaction of [2.2]paracyclophane (pcp) with silver(I) trifluoroacetate (AgCF(3)CO(2)) and silver(I) pentafluoroproprionate (AgC(2)F(5)CO(2)) has led to isolation of three novel intercalation polymers: [Ag(4)(pcp)(CF(3)CO(2))(4)](C(6)H(6)) (1), [Ag(4)(pcp)(CF(3)CO(2))(4)](C(6)H(3)Me(3)) (2), and [Ag(4)(pcp)(C(2)F(5)CO(2))(4)](pcp) (3). Structure studies using single crystal X-ray diffraction have shown that all compounds contain two-dimensional layered frameworks based on cation-pi interactions, in which pcp exhibits an unprecedented micro-tetra-eta(2) coordination mode. Guest molecules which weakly interact with the host pcp via C-H.pi interactions are intercalated between layers. The guest-eliminated complexes (1a and 2a) and guest-reincorporated ones (1b or 1c and 2b or 2c), accompanied by small structural changes, were confirmed by (1)H NMR, thermogravimetric analysis, mass spectra, and X-ray powder diffraction patterns. The structural changes from 1 --> 1a --> 1c (=1) can take place reversibly in the process of exposure of 1a to benzene vapor. The original framework of complex 2 is also completely recovered by immersing 2a in mesitylene as well as exposing it to mesitylene vapor.     

Concentration of indole in coal tar using α-cyclodextrin as the host for inclusion complexation

Inclusion complexation by -cyclodextrin (-CD) was utilized to develop a novel method of extracting indole in coal tar. An aqueous solution of -CD and a sample oil containing indole was stirred to form a solid -CD-indole complex. Both model and real sample oils were tested. Composition changes of the sample oils accompanied by the inclusion process were measured with capillary gas chromatography. -CD was found to have the remarkable characteristic of concentrating indole selectively even in a complicated mixture.