Modulation of electronic and redox properties in phenolate-rich cobalt(III) complexes and their implications for catalytic proton reduction.

We investigate the redox, spectroscopy and catalytic reactivity of new cobalt(iii) complexes based on phenolate-rich [N2O3] ligands. These complexes are described as [Co(III)(L(X))MeOH], where X indicates the presence of chloro (), bromo (), iodo (), or tert-butyl () substituents in the 3(rd) and 5(th) positions of each phenolate ring. These substituents modulate the Co(iii) ← PheO(-) LMCT bands of the parent complexes with (451) > (453) > (456) > (468 nm) and the redox potentials involved with the Co(iii)/Co(ii) and ligand reduction and with the phenolate/phenoxyl oxidation processes.

Cationic copper(II)-containing surfactants: molecular structures, film morphology, and influence on the alignment of nematic mesogens.

We discuss the synthesis and amphiphilic behavior of the cationic metallosurfactants [(L(Py14))2Cu(II)ClO4]ClO4 (1), [(L(Py16))2Cu(II)ClO4]ClO4 (2), [(L(Py18))2Cu(II)ClO4]ClO4 (3), [(L(Py18))2Cu(II)NO3]NO3 (4), [(L(Py18))2Cu(II)Cl]Cl (5), and [(L(Py18))2Cu(II)Br]Br (6) obtained by treatment of the appropriate alkylaminemethyl-2-pyridine ligand containing tetra-, hexa-, or octadecyl chains with copper salts. These metallosurfactants show excellent agreement between infrared spectroscopic bands, spectrometric masses with isotopic patterns, and elemental composition. Single-crystal X-ray data available for 1, 2, 5 and the previously published 3 reveal a trigonal bipyramidal copper(II) ion bound at the basal plane to the amine and pyridine of each alkylaminemethylpyridine ligand and an anionic coligand to the apical position.

Effect of substituents on the water oxidation activity of [Ru(II)(terpy)(phen)Cl]+ procatalysts.

A series of [Ru(II)(terpy-R)(phen-X)Cl]PF6 complexes was designed where terpy-R is the tridentate 4'-(4-methylmercaptophenyl)-2,2':6'2″-terpyridine ligand MeMPTP and phen-X is a substituted phenanthroline with hydro (1), 5-nitro (2), 5,6-dimethyl (3), and 3,4,7,8-tetramethyl (4). This series allows us to compare the reactivity of phenanthroline-containing procatalysts with that of its well-established bipyridine counterparts as well as to study the effects of electron-withdrawing and -donating substituents on water oxidation. These species were thoroughly characterized by spectroscopic and spectrometric methods, and the structures of 1, 3, and 4 were determined by single-crystal X-ray diffraction.

Inhibition of the 26S proteasome as a possible mechanism for toxicity of heavy metal species.

In this paper we report on the synthesis of five metal complexes coordinated to the [NN'O] ligand HL(iodo) (2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol), namely [Al(III)(L(iodo))2]ClO4 (1), [Cd(II)(L(iodo))Cl]·H2O (2), [Hg(II)(L(iodo))2]·4DMSO (3), [Pb(II)(L(iodo))NO3] (4), and [Sn(IV)(L(iodo))Cl3] (5). Species 1-5 are thoroughly characterized by spectroscopic and spectrometric methods, as well as by elemental analysis. X-ray crystallography results for complex 3 indicate the presence of Hg(II) ion hexacoordinated to two facially oriented [NN'O] ligands, whereas for complex 5 an Sn(IV) ion chelates to one deprotonated ligand and three chlorido coligands.

Volatile and thermally stable mid to late transition metal complexes containing α-imino alkoxide ligands, a new strongly reducing coreagent, and thermal atomic layer deposition of Ni, Co, Fe, and Cr metal films.

Treatment of MCl2 (M = Cu, Ni, Co, Fe, Mn, Cr) with 2 equiv of α-imino alkoxide salts K(RR'COCNtBu) (R = Me, tBu; R' = iPr, tBu) afforded M(RR'COCNtBu)2 or [Mn(RR'COCNtBu)2]2 in 9-75% yields. These complexes combine volatility and high thermal stability and have useful atomic layer deposition (ALD) precursor properties. Solution reactions between Ni, Co, and Mn complexes showed that BH3(NHMe2) can reduce all to metal powders.

Synthesis, structure, and solution reduction reactions of volatile and thermally stable mid to late first row transition metal complexes containing hydrazonate ligands.

Treatment of MCl2 (M = Ni, Co, Fe, Mn, Cr) with 2 equiv of the hydrazonate salts K(tBuNNCHCtBuO), K(tBuNNCHCiPrO), or K(tBuNNCMeCMeO) afforded the complexes M(tBuNNCHCtBuO)2 (M = Ni, 65%; Co, 80%; Fe, 83%; Mn, 68%; Cr, 64%), M(tBuNNCHCiPrO)2 (M = Ni, 63%; Co, 86%; Fe, 75%), and M(tBuNNCMeCMeO)2 (M = Ni, 34%; Co, 29%; Fe, 27%). Crystal structure determinations of Co(tBuNNCHCtBuO)2, M(tBuNNCHCiPrO)2 (M = Ni, Co), and M(tBuNNCMeCMeO)2 (M = Ni, Co, Fe) revealed monomeric complexes with tetrahedral geometries about the metal centers. To evaluate the potential of these new complexes as film growth precursors, preparative sublimations, thermogravimetric analyses, solid state decomposition studies, and solution reactions with reducing coreagents were carried out.

Synthesis, structure, and properties of group 1 metal complexes containing nitrogen-rich hydrotris(tetrazolyl)borate ligands.

Nitrogen-rich hydrotris(tetrazolyl)borate salts of lithium, sodium, and potassium have been prepared for the first time by thermolysis of the borohydride ion with three equivalents of tetrazoles in ether solvents at 160-162 °C. Despite the high nitrogen contents, these complexes have low sensitivity to impact, electrostatic discharge, and friction.

Volatility and high thermal stability in mid-to-late first-row transition-metal complexes containing 1,2,5-triazapentadienyl ligands.

Treatment of first-row transition-metal MCl(2) (M = Ni, Co, Fe, Mn, Cr) with 2 equiv of the potassium 1,2,5-triazapentadienyl salts K(tBuNNCHCHNR) (R = tBu, NMe(2)) afforded M(tBuNNCHCHNR)(2) in 18-73% isolated yields after sublimation. The X-ray crystal structures of these compounds show monomeric, tetrahedral molecular geometries, and magnetic moment measurements are consistent with high-spin electronic configurations. Complexes with R = tBu sublime between 155 and 175 °C at 0.

Effects of tethered ligands and of metal oxidation state on the interactions of cobalt complexes with the 26S proteasome.

In this paper we report on the synthesis and characterization of three cobalt complexes described as [Co(II)(L(1))(2)] (1), [Co(II)(L(2))] (2), and [Co(III)(L(1))(2)]ClO(4)(3). These complexes contain the deprotonated forms of the [NN'O] tridentate ligand HL(1) and its newly synthesized [N(2)N'(2)O(2)] hexadentate counterpart H(2)L(2), namely, 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol and 6,6'-((ethane-1,2-diylbis((pyridin-2-ylmethyl) azanediyl))bis(methylene))bis(2,4-diiodophenol). Characterizations for 1-3 include electrospray ionization (ESI) spectrometry, infrared, and UV-visible spectroscopies, and elemental analyses.

Poly(pyrazolyl)aluminate complexes containing aluminum-hydrogen bonds.

The treatment of LiAlH(4) with 2, 3, or 4 equiv of the 3,5-disubstituted pyrazoles Ph(2)pzH or iPr(2)pzH afforded [Li(THF)(2)][AlH(2)(Ph(2)pz)(2)] (97%), [Li(THF)][AlH(Ph(2)pz)(3)] (96%), [Li(THF)(4)][Al(Ph(2)pz)(4)] (95%), and [Li(THF)][AlH(iPr(2)pz)(3)] (89%). The treatment of ZnCl(2) with [Li(THF)][AlH(Ph(2)pz)(3)] afforded Zn(AlH(Ph(2)Pz)(3))H (70%). X-ray crystal structures of these complexes demonstrated κ(2) or κ(3) coordination of the aluminum-based ligands to the Li or Zn ions.

Modeling the geometric, electronic, and redox properties of iron(III)-containing amphiphiles with asymmetric [NN'O] headgroups.

Two iron(III)-containing amphiphiles 1 and 2 have been synthesized with the [NN'O] ligands HL(tBu-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-di-tert-butylphenol) and HL(I-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-diiodophenol), respectively. Compound 1 is monometallic, whereas EXAFS data suggest that 2 is a mixture of mono- and bimetallic species. The archetypical [Fe(III)(L(NN'O))(2)](+) complexes 3-9 have been isolated and characterized in order to understand the geometric, electronic, and redox properties of the amphiphiles.

Efficient hydride and pyrazolyl redistribution upon thermolysis of a calcium complex containing dihydrobis(pyrazolyl)borate ligands.

Thermolysis of CaBp(2)(THF)(2) (THF = tetrahydrofuran) at 190-200 °C and 0.05 Torr leads to a redistribution reaction to afford CaTp(2) (90%) and CaTp(BH(4)) (84%). Treatment of CaTp(BH(4)) with THF affords CaTp(BH(4))(THF)(2) and [CaTp(BH(4))(THF)](4), both of which were structurally characterized.

A modular approach to redox-active multimetallic hydrophobes of discoid topology.

A new modular [Fe(II)(Fe(III)L(2))(3)](PF(6))(2) species with discoid (disk-like) topology exhibits redox and surfactant properties and points to a new approach for multimetallic Langmuir film precursors.

Metals in anticancer therapy: copper(II) complexes as inhibitors of the 20S proteasome.

Selective 20S proteasomal inhibition and apoptosis induction were observed when several lines of cancer cells were treated with a series of copper complexes described as [Cu(L(I))Cl] (1), [Cu(L(I))OAc] (2), and [Cu(HL(I))(L(I))]OAc (3), where HL(I) is the ligand 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol. These complexes were synthesized, characterized by means of ESI spectrometry, infrared, UV-visible and EPR spectroscopies, and X-ray diffraction when possible. After full characterization species 1-3 were evaluated for their ability to function as proteasome inhibitors and apoptosis inducers in C4-2B and PC-3 human prostate cancer cells and MCF-10A normal cells.

Volatility and high thermal stability in tantalum complexes containing imido, amidinate, and halide or dialkylamide ligands.

Treatment of Ta(NtBu)Cl(3)(py)(2) with 2 equiv of Li(iPrNCMeNiPr) or Li(tBuNCMeNtBu) afforded Ta(NtBu)(iPrNCMeNiPr)(2)Cl and Ta(NtBu)(tBuNCMeNtBu)(2)Cl in 63% and 61% yields, respectively. Treatment of Ta(NtBu)(iPrNCMeNiPr)(2)Cl or Ta(NtBu)(tBuNCMeNtBu)(2)Cl with LiNRR' afforded Ta(NtBu)(iPrNCMeNiPr)(2)(NRR') and Ta(NtBu)(tBuNCMeNtBu)(2)(NRR') in 79-92% yields (R, R' = Me, Et). Treatment of Ta(NtBu)(tBuNCMeNtBu)(2)Cl with AgBF(4) afforded Ta(NtBu)(tBuNCMeNtBu)(2)F in 54% yield, while treatment of Ta(NtBu)(tBuNCMeNtBu)(2)Cl with BBr(3) afforded Ta(NtBu)(tBuNCMe-NtBu)(2)Br in 68% yield.

Comparative activities of nickel(II) and zinc(II) complexes of asymmetric [NN'O] ligands as 26S proteasome inhibitors.

In this study, we compare the proteasome inhibition capabilities of two anticancer candidates, [Ni(L(IA))(2)] (1) and [Zn(L(IA))(2)] (2), where L(IA-) is the deprotonated form of the ligand 2,4-diiodo-6-(((2-pyridinylmethyl)amino)methyl)phenol. Species 1 contains nickel(II), a considerably inert ion that favors covalency, whereas 2 contains zinc(II), a labile transition metal ion that favors predominantly ionic bonds. We report on the synthesis and characterization of 1 and 2 using various spectroscopic, spectrometric, and structural methods.

Volatility, high thermal stability, and low melting points in heavier alkaline earth metal complexes containing tris(pyrazolyl)borate ligands.

Treatment of MI(2) (M = Ca, Sr) or BaI(2)(THF)(3) with 2 equiv of potassium tris(3,5-diethylpyrazolyl)borate (KTp(Et2)) or potassium tris(3,5-di-n-propylpyrazolyl)borate (KTp(nPr2)) in hexane at ambient temperature afforded CaTp(Et2)(2) (64%), SrTp(Et2)(2) (64%), BaTp(Et2)(2) (67%), CaTp(nPr2)(2) (51%), SrTp(nPr2)(2) (75%), and BaTp(nPr2)(2) (39%). Crystal structure determinations of CaTp(Et2)(2), SrTp(Et2)(2), and BaTp(Et2)(2) revealed monomeric structures. X-ray structural determinations for strontium tris(pyrazolyl)borate (SrTp(2)) and barium tris(pyrazolyl)borate ([BaTp(2)](2)) show that SrTp(2) exists as a monomer and [BaTp(2)](2) exists as a dimer containing two bridging Tp ligands.

Chromium(0)-promoted [6pi + 2pi] cycloadditions of allenes with cycloheptatriene.

Photoinitiated [6pi + 2pi] cycloadditions of allenes with (eta(6)-cycloheptatriene)tricarbonylchromium(0) (1) are described. An example of asymmetric induction obtained by reaction of 1 with a chiral 1,3-disubstituted allene is also reported.

Interfacial behavior and film patterning of redox-active cationic copper(II)-containing surfactants.

Herein, we describe the synthesis and characterization of a novel series of single-tail amphiphiles LPyCn (Py=pyridine, Cn=C18, C16, C14, C10) and their copper(II)-containing complexes, which are of relevance for patterned films. The N-(pyridine-2-ylmethyl)alkyl-1-amine ligands and their complexes [CuIICl2(LPyC18)] (1), [CuIICl2(LPyC16)] (2), [CuIICl2(LPyC14)] (3), [CuIIBr2(LPyC18)] (4), [CuIIBr2(LPyC16)] (5), and [CuIIBr2(LPyC10)] (6) were synthesized, isolated, and characterized by means of mass spectrometry, IR and NMR spectroscopies, and elemental analysis. Complexes 1, 2, 3, and 6 had their molecular structure solved by X-ray diffraction methods, which showed that the local geometry around the metal center is distorted square planar.

Synthesis of the chiral tripyridyldiamine ligand Bn-CDPy3 and characterization of its Co(III) complex [Co(Bn-CDPy3)Cl]Cl2.

Synthesis of the tripyridyldiamine Bn-CDPy3, a chiral pentadentate ligand, and characterization of its low-spin Co(III) complex [Co(Bn-CDPy3)Cl]Cl2 by X-ray crystallography, 1H NMR, 13C NMR, IR and UV-vis spectroscopy as well as molar conductivity and mass spectrometry, is described.

Effects of excited state-excited state configurational mixing on emission bandshape variations in ruthenium-bipyridine complexes.

The 77 K emission spectra of 21 [Ru(L) 4bpy] ( m+ ) complexes for which the Ru/bpy metal-to-ligand-charge-transfer ( (3)MLCT) excited-state energies vary from 12 500 to 18 500 cm (-1) have vibronic contributions to their bandshapes that implicate excited-state distortions in low frequency ( lf; hnu lf < 1000 cm (-1)), largely metal-ligand vibrational modes which most likely result from configurational mixing between the (3)MLCT and a higher energy metal centered ( (3)LF) excited state. The amplitudes of the lf vibronic contributions are often comparable to, or sometimes greater than those of medium frequency ( mf; hnu mf > 1000 cm (-1)), largely bipyridine (bpy) vibrational modes, and for the [Ru(bpy) 3] (2+) and [Ru(NH 3) 4bpy] (2+) complexes they are consistent with previously reported resonance-Raman (rR) parameters. However, far smaller lf vibronic amplitudes in the rR parameters have been reported for [Os(bpy) 3 ] (2+), and this leads to a group frequency approach for interpreting the 77 K emission bandshapes of [Ru(L) 4bpy] ( m+ ) complexes with the vibronic contributions from mf vibrational modes referenced to the [Os(bpy) 3] (2+) rR parameters (OB3 model) and the envelope of lf vibronic components represented by a "progression" in an "equivalent" single vibrational mode ( lf1 model).

Influence of the apical ligand in the thermotropic mesomorphism of cationic copper-based surfactants.

A new pyridine-based bidentate ligand L (PyC18) was used to develop copper-containing surfactants that exhibit mesomorphism. Complexes [(L (PyC18)) 2Cu (II)Y]Y were synthesized, where Y is an anionic ligand bromo ( 1), nitrato ( 2), or perchlorato ( 3). The nature of these apical ligands determines the mesogenic behavior of 1- 3: The smallest bromo-substituted species 1 shows a metastable liquid crystalline phase at 110 degrees C, the nitrato-substituted 2 increases the transition temperature to 136 degrees C, and the bulky perchlorato-substituted 3 shows reversible mesophases at 153 degrees C.

Synthesis, redox, and amphiphilic properties of responsive salycilaldimine-copper(II) soft materials.

Hydrolysis of the asymmetric pyridine- and phenol-containing ligand HL (1) (2-hydroxy-4-6-di- tert-butylbenzyl-2-pyridylmethyl)imine) led to the use of bis-(3,5-di -tert-butyl-2-phenolato-benzaldehyde)copper(II), [Cu (II)(L (SAL)) 2] ( 1) as a precursor for bis-(2,4-di- tert-butyl-6-octadecyliminomethyl-phenolato)copper(II), [Cu (II)(L (2)) 2] ( 3), bis-(2,4-di- tert-butyl-6-octadecyl aminomethyl-phenolato)copper(II), [Cu (II)(L (2A)) 2] ( 3'), and bis-(2,4-di- tert-butyl-6-[(3,4,5-tris-dodecyloxy-phenylimino)-methyl]-phenolato)copper(II), [Cu (II)(L (3)) 2] ( 4). These complexes exhibit hydrophilic copper-containing head groups, hydrophobic alkyl and alkoxo tails, and present potential as precursors for redox-responsive Langmuir-Blodgett films. All systems were characterized by means of elemental, spectrometric, spectroscopic, and electrochemical techniques, and their amphiphilic properties were probed by means of compression isotherms and Brewster angle microscopy.

Amphiphilic and magnetic properties of a new class of cluster-bearing [L2Cu4(mu4-O)(mu2-carboxylato)4] soft materials.

A general approach toward amphiphilic systems bearing multimetallic clusters and their ability to form Langmuir-Blodgett films is presented. The synthetic strategy to stabilize these clusters involves the use of a ligand (HL) containing an N(2)O-donor set and long octadecanoic chains to obtain the carboxylate-supported [L(2)Cu(4)(mu(4)-O)(mu(2)-OAc)(4)]EtOH (1) and [L(2)Cu(4)(mu(4)-O)(mu(2)-OBz)(4)] (2) in which OAc(-) and OBz(-) represent acetate (1) and benzoate (2) co-ligands. These species were thoroughly characterized and had their structures solved by X-ray crystallography.