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. The influence of the substituents on the phenolate pendant arms was also observed on the kinetic parameters; presented a rate constant of 1.0 × 10(-3) s(-1) whereas showed a considerably slower rate (5.3 × 10(-5) s(-1)). Species and are electrocatalysts towards proton reduction in the presence of weak acid in acetonitrile. A TON of 10.8 was observed for after 3 h of bulk electrolysis at -2.20 VFc/Fc(+) using a mercury pool as the working electrode.

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. Except for the surfactant with the shortest tetradecyl (C14) chain, these species yield Langmuir films with collapse pressures of 45-55 mN·m(-1) and average areas of ca. 50 Å(2). A plateau around 15 mN·m(-1) is observed for 3, 4, and 5 and associated with the formation of dendritic domains about 50 µm in size. Species 2 and 6 lack this plateau and show domains of ca. 5 µm. Once transferred onto solid substrates, the resulting Langmuir-Blodgett film of 3 at 18 mN·m(-1) influences the alignment of the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline.

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. The procatalysts 1-4 show opposite trends compared to known terpyridine/bipyridine species; the unsubstituted procatalyst 1 yields a turnover number (TON) of 410 followed by 250 and 150 for complexes 3 and 4 with electron-donating substituents. Species 2, with electron-withdrawing properties, yields the lowest TON of 60. Although the TONs decrease upon substitution, the presence of electron-donating methyl substituents enhances the rate of O2 evolution during an early stage of catalysis. Interestingly, no evidence of conversion from chlorido-containing procatalysts into expected aqua-containing catalysts was observed for 1-4 by NMR and UV-visible spectroscopy during the induction period. This observation, along with reactivity toward (NH4)2[Ce(IV)(NO3)6], suggests that water nucleophilic attack happens to a high-valent ruthenium species rather than while at the Ru(II) oxidation state. Reactivity follows a trend similar to the rate of O2 evolution in all complexes. Furthermore, the electrospray ionization mass spectrometry and (1)H NMR analyses of 1, as recovered after catalysis, indicate the presence of a chlorido ligand.

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. The toxicity of species 1-5 is tested against transformed human prostate epithelial cells CRL2221 and we observe that the five complexes demonstrate high levels of cell growth inhibition in a dose-dependent manner. In order to evaluate the relationship between these species and the proteasome, we test 1-5 against purified 20S, CRL2221 cell extracts, and intact cells, followed by the measurement of the percent chymotrypsin-like activity inhibition levels. Results suggest a good correlation between the toxicity of [Hg(II)(L(iodo))2]·4DMSO (3) and proteasome inhibition.

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. ALD growth of Ni, Co, Fe, and Cr films is demonstrated. Mn film growth may be possible, but the films oxidize completely upon exposure to air.

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. M(tBuNNCHCtBuO)2 sublime between 120 and 135 °C at 0.05 Torr, whereas M(tBuNNCHCiPrO)2 and M(tBuNNCMeCMeO)2 sublime between 100 and 105 °C at the same pressure. All complexes afforded ≥96% recovery of sublimed material, with ≤3% of nonvolatile residues. The solid state decomposition temperatures were highest for M(tBuNNCHCiPrO)2 (273-308 °C), intermediate for M(tBuNNCHCtBuO)2 (241-278 °C), and lowest for M(tBuNNCMeCMeO)2 (235-250 °C). Treatment of Co(tBuNNCHCtBuO)2 in tetrahydrofuran with hydrazine, BH3(L) (L = NHMe2, SMe2, THF), pinacol borane, and LiAlH4 led to rapid formation of cobalt metal, while analogous reductions of Mn(tBuNNCHCtBuO)2 with BH3(THF), pinacol borane, and LiAlH4 appeared to afford manganese metal. The new complexes M(tBuNNCHCtBuO)2, M(tBuNNCHCiPrO)2, and M(tBuNNCMeCMeO)2 have very promising properties for use as precursors for the growth of the respective metals in atomic layer deposition film growth processes.

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 0.05 Torr and have decomposition temperatures that range from 280 to 310 °C, whereas complexes with R = NMe(2) sublime at 105 °C at 0.05 Torr but decompose between 181 and 225 °C. This work offers new nitrogen-rich ligands that are related to widely used ß-diketiminate and 1,3,5-triazapentadienyl ligands and demonstrates new complexes with properties suitable for use in atomic-layer deposition.

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. A detailed (1)H-NMR study was conducted for 3 and X-ray structural data was obtained for 2. The viability of this series as potential agents for proteasome inhibition and cell apoptotic induction involving PC-3 cancer cells is presented comparing the behavior of the untethered [NN'O](2) six-coordinate 1 and 3 and the tethered counterpart 2 with a 1:1 metal-to-ligand ratio. It is observed that the tethering in 2 decreases inhibition activity. When 1 and 3 are compared, the most inert, but redox-active, cobalt(III) species shows the highest chymotrypsin-like activity inhibition on purified proteasome and PC-3 cancer cells. A hypothesis based on the role of oxidation states for proteasome inhibition is offered.

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. The treatment of [Li(THF)][AlH(Ph(2)pz)(3)] with MgBr(2) or CoCl(2) in THF/Et(2)O solutions, by contrast, afforded the pyrazolate transfer products Mg(2)Br(2)(Ph(2)pz)(2)(THF)(3)·2THF (25%) and Co(2)Cl(2)(Ph(2)pz)(2)(THF)(3)·THF (23%) as colorless and blue crystalline solids, respectively. An analogous treatment of [Li(THF)][AlH(Ph(2)pz)(3)] with MCl(2) (M = Mn, Fe, Ni, Cu) afforded metal powders and H(2), illustrating hydride transfer from Al to M as a competing reaction path.

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. Preference for a monometallic or bimetallic nuclearity is dependent on (i) the nature of the solvent used for synthesis and (ii) the type of the substituent in the phenol moiety. In methanol, the tert-butyl-, methoxy-, and chloro-substituted 3, 4, and 5 are monometallic species, whereas the bromo- and iodo-substituted 6 and 7 form bimetallic complexes taking advantage of stabilizing methoxo bridges generated by solvent deprotonation. In dichloromethane, the bromo- and iodo-substituted 8 and 9 are monometallic species; however, these species favor meridional coordination in opposition to the facial coordination observed for the tert-butyl- and methoxy-substituted compounds. Molecular structures for species 5, 7, 8, and 9 have been solved by X-ray diffraction. Furthermore, the electronic spectrum of the amphiphile 1 was expected to be similar to those of facial/cis archetypes with similar substituents, but close resemblance was observed with the profile for those meridional/cis species, suggesting a similar coordination mode. This trend is discussed based on DFT calculations, where preference for the meridional/cis coordination mode appears related to the presence of tertiary amine nitrogen on the ligand, as when a long alkyl chain is attached to the [NN'O] headgroup.

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. Methanolysis or ethanolysis/hydrolysis of the BH(4)(-)-containing complexes affords [TpCa(HOMe)(2)(µ(4)-B(OMe)(4))Ca(HOMe)(2)Tp][B(OMe)(4)] and [{TpCa}(3){µ(6)-B(OB(OEt)(3))(3)]·EtOH.

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.

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. X-ray crystal structures of Ta(NtBu)(tBuNCMeNtBu)(2)F and Ta(NtBu)(tBuNCMeNtBu)(2)Br revealed that the amidinate ligands exhibit eta(2)-coordination, and that the imido and halide ligands are cis to each other within the distorted octahedral structures. NMR studies indicated that the other complexes have analogous structures. Additionally, variable temperature NMR studies revealed that some of the complexes undergo amidinate rearrangement. The enthalpies, entropies, and free energies of activation for these rearrangements were calculated for Ta(NtBu)(tBuNCMeNtBu)(2)X (X = F, Cl, Br). When X = F, DeltaH(double dagger) = 9.1 +/- 0.4 kcal/mol, DeltaS(double dagger) = -20.5 +/- 1.6 cal/mol x K, and DeltaG(double dagger)(298 K) = 15.3 +/- 0.7 kcal/mol. For X = Cl, DeltaH(double dagger) = 12.4 +/- 0.3 kcal/mol, DeltaS(double dagger) = -20.2 +/- 0.8 cal/mol x K, and DeltaG(double dagger)(298 K) = 18.4 +/- 0.3 kcal/mol. When X = Br, DeltaH(double dagger) = 12.5 +/- 0.5 kcal/mol, DeltaS(double dagger) = -21.7 +/- 1.5 cal/mol x K, and DeltaG(double dagger)(298 K) = 19.0 +/- 0.7 kcal/mol. All of the complexes are volatile, and they sublime between 120 and 203 degrees C. In addition, Ta(NtBu)(iPrNCMeNiPr)(2)NMe(2) has a decomposition point that is 65-160 degrees C higher than widely used film growth precursors and is therefore a promising candidate for use in chemical vapor deposition and atomic layer deposition film growth techniques.

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. Furthermore, the pharmacological effects of 1 and 2, along with those of the salts NiCl(2) and ZnCl(2), were evaluated in vitro and in cultured human cancer cells in terms of their proteasome-inhibitory and apoptotic cell-death-inducing capabilities. It is shown that neither NiCl(2) nor 1 have the ability to inhibit the proteasome activity at any sustained levels. However, ZnCl(2) and 2 showed superior inhibitory activity versus the chymotrypsin-like activity of both the 26S proteasome (IC(50) = 5.7 and 4.4 micromol/L, respectively) and the purified 20S proteasome (IC(50) = 16.6 and 11.7 micromol/L, respectively) under cell-free conditions. Additionally, inhibition of proteasomal activity in cultured prostate cancer cells by 2 was associated with higher levels of ubiquitinated proteins and apoptosis. Treatment with either the metal complex or the salt was relatively nontoxic toward human normal cells. These results strengthen the current working hypothesis that fast ligand dissociation is required to generate an [ML(IA)](+) pharmacophore, capable of interaction with the proteasome. This interaction, possibly via N-terminal threonine amino acids present in the active sites, renders the proteasome inactive. Our results present a compelling rationale for 2 along with its gallium(III) and copper(II) congeners to be further investigated as potential anticancer drugs that act as proteasome inhibitiors.

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. With distinct stoichiometries and protonation states, this series suggests the assignment of species [CuL(I)](+) as the minimal pharmacophore needed for proteasomal chymotryspin-like activity inhibition and permits some initial inference of mechanistic information.

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. The thermogravimetric analysis traces, preparative sublimations, and melting point/decomposition determinations demonstrate generally very high thermal stabilities and reasonable volatilities. SrTp(2) has the highest volatility with a sublimation temperature of 200 degrees C/0.05 Torr. [BaTp(2)](2) is the least thermally stable with a decomposition temperature of 330 degrees C and a percent residue of 46.5% at 450 degrees C in the thermogravimetric analysis trace. SrTp(Et2)(2), BaTp(Et2)(2), CaTp(nPr2)(2), SrTp(nPr2)(2), and BaTp(nPr2)(2) vaporize as liquids between 210 and 240 degrees C at 0.05 Torr. BaTp(Et2)(2) and BaTp(nPr2)(2) decompose at about 375 degrees C, whereas MTp(Et2)(2) and MTp(nPr2)(2) (M = Ca, Sr) are stable to >400 degrees C. Several of these new complexes represent promising precursors for chemical vapor deposition and atomic layer deposition film growth techniques.

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. With the aim of using these species as precursors for redox-responsive films, an assessment of their electrochemical properties involved cyclic voltammetry in different solvents, with different supporting electrolytes and scan rates. Density functional theory calculations of relevant species in bulk and at interfaces were used to evaluate their electronic structure and dipole moments. The morphology and order of the resulting films at the air/water interface were studied by isothermal compression and Brewster angle microscopy. Biphasic patterned Langmuir films were observed for all complexes except 3 and 6, and dependence on the chain length and the nature of the halogen coligand determine the characteristics of the isotherms and their intricate topology. Complexes 3 and 6, which have shorter chain lengths, failed to exhibit organization. These results exemplify the first comprehensive study of the behavior of single-tail metallosurfactants, which are likely to lead to high-end technological applications based on their patterned films.