Tailor made synthesis of amphiphilic azoaromatics via regioselective C–N bond fusion. Comparative studies of surface properties of the two positional isomers and cobalt complexes (original) (raw)
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Inorganic Chemistry, 2007
The stabilization of a bivalent oxidation state in cobalt complexes of phenolate-based asymmetric tridentate ligands with iodo and bromo substituents is studied. The complexes [Co II (L IA ) 2 ]‚2CH 3 OH (1) and [Co II (L BrA ) 2 ]‚CH 3 OH (2) were characterized by means of several spectroscopic and spectrometric techniques. The molecular structure of 1 was determined by diffractometric analysis and reveals the cobalt(II) ion in a distorted-octahedral geometry. The centrosymmetric metal ion adopts a local D 2h symmetry and is surrounded by facially coordinated ligands. Equivalent donor sets in both ligands are trans to each other, and DFT calculations suggest that the fac−trans configuration is favored by a small margin when compared to the fac−cis isomers. Both DFT calculations and EPR spectroscopy agree with a high-spin S ) 3 / 2 electronic configuration given by [a g 1 , b 1g 1 , a g 1 , b 2g 2 , b 3g 2 ]. This oxidation state was indirectly observed by the lack of a pπ phenolate f dσ* cobalt(III) charge-transfer band, which is found between 430 and 470 nm for similar cobalt(III) species. On the basis of the geometrical preferences and the oxidation state of archetypical 1 and 2, two metallosurfactants [Co II (L I-ODA ) 2 ] (3) and [Co II (L I-NOBA ) 2 ].CH 2 Cl 2 (4) were obtained. The redox chemistry of 1−4 is marked by metal-and ligand-centered activity with several follow up processes and film formation on the electrode. Both metallosurfactants exhibit amphiphilic properties and organization, as shown by compression isotherms and Brewster angle microscopy but exhibit dissimilar collapse mechanisms; whereas 3 collapses at constant pressure, 4 exhibits a constant-area collapse. Langmuir−Blodgett films are readily obtained and were characterized by equilibrium contact angle and atomic force microscopy. Fallis, I. A.; Chuenpratoom, T.; Watanesk, R. AdV. Colloid Interface Sci. 2006, 122, 107. (3) Domonguez-Gutierrez, D.; Surtchev, M.; Eiser, E.; Elsevier, C. Hofmeyer, H.; Newkome, G. R. Modern Terpyridine Chemistry; Wiley-VCH: Weinheim, Germany, 2006. (8) Park, J.; Pasupathy, A. N.; Goldsmith, J. I.; Chang, C.; Yaish, Y.; Petta, J. R.; Rinkoski, M.; Sethna, J. P.; Abruna, H. D.; McEuen, P. L.; Ralph, D. C. Nature 2002, 417, 722. (9) Hjelm, J.; Handel, R. W.; Hagfeldt, A.; Constable, E. C.; Housecroft, C. E.; Forster, R. (23) Imbert, C.; Hratchian, H. P.; Lanznaster, M.; Heeg, M. J.; Hryhorczuk, L. M.; McGarvey, B. R.; Schlegel, H. B.; Verani, C. N. Inorg. Chem. 2005, 44, 7414-7422. (24) Neves, A.; Romanowski, S. M.; Vencato, I.; Mangrich, A. S.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
We report studies of a newly synthesized cyclam derivative with four chain substituents (tetra-(N-2-tetradecylcarboxamidoethyl )-tetraazacyclotetradecane; TC14) which could be of interest for the selective liquid-liquid extraction of cations. We investigated the monolayer properties of TC14 molecules spread at the aqueous solution/air interface by surface pressure-area isotherm measurements and Brewster angle microscopy. Surface pressure-area isotherms measurements were also performed at the aqueous solution/decane interface with a new interfacial Langmuir trough. The effects of the salt concentration in solutions (CuCl 2 , NaCl and CsCl ) on the TC14 surface pressure-area isotherms were related to the binding of the cations to the cage molecule at the interface. It was found that the film was sensitive to the presence of ions in the aqueous phase, particularly in the high-pressure region of the isotherm, where the film collapses. The Langmuir balance technique revealed the preferential complexation of Cu2+ ions by the cage molecule in the interface and permitted us to detect the presence of very small ion concentrations in the subphase.
Inorganic Chemistry, 2004
The synthesis of the new terpyridine-containing macrocycle 2, 5,8,11,14-pentaaza[15](6,6′′)cyclo(2,2′:6′,2′′)terpyridinophane (L) is reported. The ligand contains a pentaamine chain linking the 6,6′′ positions of a terpyridine unit. A potentiometric, 1 H NMR, UV−vis spectrophotometric and fluorescence emission study on the acid−base properties of L in aqueous solutions shows that the first four protonation steps occur on the polyamine chain, whereas the terpyridine nitrogens are involved in proton binding only at strongly acidic pH values. L can form both mono-and dinuclear Cu(II), Zn(II), Cd(II), and Pb(II) complexes in aqueous solution. The crystal structures of the Zn(II) and Cd(II) complexes {[ZnLH] 2 (µ-OH)}(ClO 4 ) 5 (6) and {[CdLH] 2 (µ-Br)}(ClO 4 ) 5 ‚4H 2 O (7) show that two mononuclear [MLH] 3+ units are coupled by a bridging anion (OHin 6 and Brin 7) and π-stacking interactions between the terpyridine moieties. A potentiometric and spectrophotometric study shows that in the case of Cu(II) and Zn(II) the dimeric assemblies are also formed in aqueous solution containing the ligand and the metals in a 1:1 molar ratio. Protonation of the complexes or the addition of a second metal ion leads to the disruption of the dimers due to the increased electrostatic repulsions between the two monomeric units. Jensen, P.; Kepert, C. M.; Spiccia, L. Inorg. Chem. 2003, 42, 5637-5644. (c) Fry, F. H.; Moubaraki, B.; Murray, K. S.; Spiccia, L.; Warren, M.; Skelton, B. W.; White, A. H. Miranda, C.; Navarro, P.; Escartí, F.; García-España,E.; LaTorre, J.; Ramírez, J. A. Chem. Commun. 2000, 1337-1338. (b) Lamarque, L.; Navarro, P.; Miranda, C.; Aran, V. J.; Ochoa, C.; Escartí, F.; García-España, E.; LaTorre, J.; Luis, S. V.; Miravet, Dapporto, P.; Formica, M.; Fusi, V.; Giorgi, L.; Guerri, A.; Micheloni, M.; Paoli, P.; Pontellini, R.; Rossi, P. Chem.s Eur. J. 2003, 9, 800-810. (b) Dapporto, P.; Formica, M.; Fusi, V.; Giorgi, L.; Micheloni, M.; Paoli, P.; Pontellini, R.; Rossi, P. Inorg. Chem. 2001, 40, 6186-6192. (13) Guerriero, P.; Tamburini, S.; Vigato, P. A. Coord. Chem. ReV. 1995, 139, 17-243. (14) Izatt, R. M.; Pawlak, K.; Bradshaw, J. S.; Bruenig, R. L. Chem. ReV. 1991, 91, 1721-1985. (15) (a) Fabbrizzi, L.; Licchelli, M.; Rabaioli, G.; Taglietti, A. Coord. Chem. ReV. 2000, 205, 85-108. (b) Fabbrizzi, L.; Licchelli, M.; Pallavicini, P. Acc. Chem. Res. 1999, 32, 846-853. (c) Fabbrizzi, L.; Licchelli, M.; Taglietti, A. J. Chem. Soc., Dalton Trans. 2003, 3471-3479. (d) Amendola, V.; Fabbrizzi, L.; Mangano, C.; Pallavicini, P. Struct. Bonding (Berlin) 2001, 99, 79-115 (e) Hortala, M. A.; Fabbrizzi, L.; Marcotte, N.; Stomeo, F.; Taglietti, A. J. Am. Chem. Soc. 2003, 125, 20-21. (16) (a) Blake, A. J.; Demartin, F.; Devillanova, F. A.; Garau, A.; Isaia, F.; Lippolis, V.; Schröder, M.; Verani, G. J. Chem. Soc., Dalton Trans. 1996, 3705-3712. (b) Blake, A. J.; Casabo, J.; Devillanova, F. A.; Escriche, L.; Garau, A.; Isaia, F.; Lippolis, V.; Kivekas, R.; Muns, V.; Schröder, M.; Sillampää, R.; Verani, G. J. Chem. Soc., Dalton Trans. 1999, 1085-1092. (c) Arca, M.; Blake, A. J.; Casabo, J.; Demartin, F.; Devillanova, F. A.; Garau, A.; Isaia, F.; Lippolis, V.; Kivekas, R.; Muns, V.; Schröder, M.; Verani, G.; J. Chem. Soc., Dalton Trans. 2001, 1180-1188. (17) (a) Azéma, J.; Galaup, C.; Picard, C.; Tisnès, P.; Ramos, P.; Juanes, O.; Rodrìguez-Ubis, J. C.; Brunet, E. Tetrahedron 2000, 56, 2673-2681 and references therein. (b) Galaup, C.; Carrié, M.-C.; Tisnès, P.; Picard, C. Eur.
Monolayers of Chiral Imidazole Amphiphiles: Domain Formation and Metal Complexation
Langmuir, 1994
The monolayer characteristics of achiral and chiral imidazole amphiphiles on the air-water interface have been studied by measuring the surface pressure/surface area (II/A) isotherms and by epifluorescence microscopy. Both types of amphiphiles form stable monolayers at the air-water interface with a welldefined liquid-expanded (LE) to liquid-condensed (LC) phase transition. The enantiomerically pure imidazole amphiphiles display the same 11/A isotherms within experimental error. The addition of small concentrations (10-6-10~* M) of transition metal ions (Co(II), Ni(II), Zn(II), and Cu(II)) causes a change in the isotherms, which suggests that these ions bind to the imidazole ligand functions. Epifluoroescence microscopy experiments on monolayers of the imidazole amphiphiles on pure water reveal that Bolid domains are formed when the monolayers are compressed into the LE to LC phase transition region. These domains have dendritic or fractal shapes. Interestingly, in the case of the chiral imidazole amphiphiles the solid domains have a chiral appearance: they turn clockwise or counterclockwise depending on the configuration of the chiral center in the amphiphile. The formation of solid domains is also observed when the chiral imidazole amphiphiles are spread on a subphase containing zinc(II) ions. These domains, however, have no chiral appearance.
Dalton Transactions, 2003
Amphiphilic cobalt() cage complexes with bridgehead octyl, dodecyl and hexadecyl hydrocarbon chain substituents have been synthesized simply by co-condensation of formaldehyde and long chain aliphatic aldehydes with the tripodal cobalt() hexaamine complex, [Co(sen)] 3ϩ {sen = 4,4Ј,4Љ-ethylidynetris(3-azabutan-1-amine)}. The synthetic methodology was also used to prepare a novel chiral surfactant by capping the Λ-(Ϫ) D-[Co(sen)] 3ϩ stereoisomer. The cobalt() cage complexes with octyl to hexadecyl substituents are all surface active and reduce the surface tension of water to levels approaching those of organic solvents. The dodecyl substituted cage complex forms aggregates in aqueous solution with a critical micelle concentration of (1.3 ± 0.1) × 10 Ϫ3 mol dm Ϫ3 at 25.00 ЊC. The surfactant cage complexes are biologically active and are lethal at millimolar levels to the tapeworm Hymenolepis diminuta, and the parasitic eukaryote, Tritrichomonas foetus, in vitro. The biological activity of these surfactants appears to involve insertion of the paraffin tail into the organism's exterior membrane and consequent incorporation of the highly charged head-group, which perturbs the normal membrane potential and leads to disintegration of the membrane and death of the organism. The cobalt() cage head-group of these surfactants also undergoes a chemically reversible one-electron reduction to the corresponding cobalt() cage complex and the construction of oriented films of such redox reagents should be feasible. The reduction potential of the cobalt()/() couple is shifted from Ϫ0.72 to Ϫ0.61 V (vs. saturated calomel electrode) by replacing a bridgehead hydrocarbon chain substituent with an alkoxy substituent. The shift in potential correlates with the electrochemical polar substituent constants of alkyl versus alkoxy chains.
Journal of Solid State Chemistry, 2001
The reactions of CoX 2 (X ؍ Br, Cl) with the planar, bidentate bridging ligand 2,1,3-benzothiadiazole (btd) in Me 2 CO led to the 2D coordination polymers +[CoBr 2 (btd)], n (1) and +[CoCl 2 (btd)], n (2). The structure of 1 was determined by singlecrystal X-ray crystallography. Complex 1 (C 6 H 4 Br 2 CoN 2 S, monoclinic, P2 1 /m, a ؍ 3.742(3), b ؍ 13.075(9), c ؍ 9.092(6) A s , ؍ 90.09(2)3, Z ؍ 2, +2 , R 1 ؍ 0.0298, wR 2 ؍ 0.0793) consists of +[Co( -Br) 2 ], n linear chains running along the a axis linked via -btd ligands along the b axis. The columns of stacked btd molecules present in the crystal structure of the free ligand are maintained in the lattice of 1. XRD data revealed that 2 is isostructural with 1. The magnetic properties of both complexes can be explained by the presence of a very weak ferromagnetic intrachain Co2Co exchange interaction through the ( -X) 2 bridges and a moderate antiferromagnetic Co2Co interaction through the -btd bridges. The new complexes were also characterized by EPR, IR, and UV/VIS spectra, and all data are discussed in terms of the nature of bonding and known structures.
A study of the second coordination sphere in 8-azaxanthinato salts of divalent metal aquacomplexes
Inorganica Chimica Acta, 2009
The interaction of the 4,6-dimethyl and 4-monomethyl derivatives of 1,2,3-triazolo[4,5-d]pyrimidin-5,7dione (which may be named also as purine derivatives, 1,3-dimethyl-8-azaxanthine, Hdmax and 3-methyl-8-azaxanthine, H3max) with the divalent cations of Mn, Co, Ni, Zn and Cd in aqueous media generate solids with formulation ML 2 Á 6H 2 O. The crystal structure of the Mn and Cd compounds with dmax and the Cd compound with 3max have been determined by single-crystal X-ray diffraction revealing that the compounds are salts with [M(H 2 O) 6 ] 2+ as cations and dmax À or 3dmax À as anions. The second-sphere interactions in these compounds have been analysed, consisting in a network of very welldefined hydrogen bonds, with all available potential donor and acceptor positions involved. The topology of the motifs generated by these hydrogen bonds has been characterised, adapting to the second coordination sphere concepts usually applied to the first (chelate, bridge, monodentate, . . .). Monodimensional (tapes) superstructures with the building blocks rather tightly bounded appear in the compounds with dmax À as anion, whereas the corresponding superstructure in the Cd compound with 3max À is bidimensional. These superstructures further interact among them in a less tight fashion to generate the three dimensional crystal structures. Powder X-ray diffraction strongly suggests that Mn, Co, Zn and Cd compounds of each ligand are isostructural, so the results of the samples determined by single-crystal X-ray diffraction may be extended to all these compounds. On the other hand, powder X-ray diffraction indicates that the nickel compounds have a different structure and the spectroscopic data for these compounds suggest that the ligand is directly attached to the metal for them.
Nanoprocessability of a one-dimensional oxalato-bridged cobalt(II) complex with 1,2,4-triazole
Inorganica Chimica Acta, 2007
The polymer {[Co(ox)(Htr)2] · 2H2O}n (ox = oxalate dianion; Htr = 1,2,4-triazole) (1) has been synthesized and characterized by FT-IR spectroscopy, thermal analysis, variable-temperature magnetic measurements and X-ray diffraction methods. The physical analysis allows us to propose a one-dimensional structure in which [Co(Htr)2]2+ units are bridged by bis-bidentate oxalato ligands. Magnetic measurements at variable temperature show an overall antiferromagnetic behavior of the compound. Isolated chains of this polymer have been obtained by sonication of 1 in water and deposition on mica or on mica treated with poly-l-lysine. Circular molecules and nano-fibres have been isolated on Highly Oriented Pyrolitic Graphite (HOPG) by casting deposition of sonicated solutions of 1 in ethanol. The direct reaction on HOPG surface between CoII, H2ox and Htr has proved a useful route to isolate one-dimensional systems on surfaces. The development of new strategies to characterize these types of polymers on surfaces opens the possibility to perform nano-scale studies on their properties and their potential use as nano-materials.Single chains, circular molecules and nano-fibres have been isolated on several surfaces by casting deposition of sonicated suspensions of {[Co(ox)(Htr)2] · 2H2O}n (1). The direct reaction between the three building blocks of the polymer allows isolating one-dimensional systems on HOPG surface. The isolation of architectures derived from these types of polymers on surfaces makes it feasible to perform nano-scale studies.
Monolayers of Bolaform Amphiphiles: Influence of Alkyl Chain Length and Counterions
Langmuir, 1994
We have prepared self-assembled monolayers of novel cationic bolaform amphiphiles on negatively charged substrates. Most of these amphiphiles form smooth, defect-free monolayers which can be used to reverse the substrate surface charge and thus allow subsequent adsorption of anionic molecules and construction of multilayers. Atomic force microscopy, surface force measurement, and surface plasmon spectroscopy were combined to probe the molecular orientation and ordering, mechanical properties, and surface electrical properties of the monolayers. In addition, the amphiphile aggregation behavior at an air-water interface was studied by surface tension measurement, and lyotropic phase behavior was studied by polarization microscopy. Our study suggests that monolayer interfacial and bulk properties can be controlled to a certain degree by selective variation of amphiphile chemical structure, in particular, the alkyl chain length and the type of counterions. An increase in alkyl chain length assists close-packing at the liquid-solid interface and self-assembly in a liquid medium due to a favorable hydrophobic free energy change. Exchange of halide ions with the strongly associating salicylate ions reduces electrostatic repulsion between head groups and also favors self-assembly and close-packing. Our study suggests that it is possible to overcome the dominance and limitation of the substrate electrostatic effect on monolayer structure by using amphiphiles with a strong inherent tendency for close-packing. Our observations contribute to the understanding of two-dimensional topochemical photopolymerization, multilayer deposition of alternating surface charges, modification of hydrophilic surface electrical properties, and in general, the dependence of monolayer architecture on molecular chemical structure and intermolecular forces.