Véronique Bulach

Molecular tectonics: from enantiomerically pure sugars to enantiomerically pure triple stranded helical coordination network

The self-assembly between a bis-monodentate tecton based on two pyridine units connected to an enantiomerically pure isomannide stereoisomer and HgCl2 leads to the formation of an enantiomerically pure triple stranded helical infinite coordination network which was structurally characterised by X-ray diffraction on single crystal.

Molecular tectonics and supramolecular chirality: rational design of hybrid 1-D and 2-D H-bonded molecular networks based on bis-amidinium dication and metal cyanide anions

Using the bis-amidinium dication 1 bearing four acidic protons disposed in a divergent fashion and capable of chelating, through H-bonds, metal cyanide anions, neutral 1- and 2-D hybrid networks were generated. Whereas in the presence of M(CN)42− (M = Ni(II), Pd(II) and Pt(II)), 1-D H-bonded networks are formed through a double dihapto mode of H-bonding between the dication and the dianion, in the case of M(CN)64− (M = Fe(II) and Ru(II)), 2-D networks based on the interconnection by the dication 1 of 1-D networks analogous to those formed in the case of [M(CN)4]2− mentioned above are obtained. Interestingly, in the case of [M(CN)6]3− (M = Cr(III)), again a 2-D H-bonded network is formed through the formation of three dihapto modes of H-bonding between the dication and the trianion. Due to this dihapto or chelate mode of H-bonding, a supramolecular chirality of the Δ′ and Λ′ type is generated within the second coordination sphere of the metallic centres. The packing of the achiral 2-D networks thus obtained leads to channels which are occupied by water molecules forming polymeric H-bonded chains.

1‐ and 2‐D Coordination Networks Based on Porphyrin and Copper: an Example of Supramolecular Isomerism

A high-yield synthesis of atropoisomers of the meso-tetrakis(o-isonicotinoylamidophenyl)porphyrin was achieved. Depending on the crystallising solvent system, the α2β2 atropoisomer leads to the formation of either 1-D or 2-D coordination networks in the presence of Cu(OAc)2.

Coordination polymers based on porphyrin and copper: the influence of the crystallization solvents on the dimensionality of the network

The α2β2 atropoisomer of meso-tetrakis(o-nicotinoylamidophenyl)–copper porphyrin leads in the presence of Cu(II) cation to coordination polymers in the crystalline phase. The networks are generated by interconnection of metalloporphyrin units through the coordination of Cu centres adopting an octahedral coordination geometry by two pyridines belonging to consecutive complexes. Depending on the solvent systems used, the 1-D coordination network based on 1α2β2 and Cu dication was shown to form a 3-D network based on a combination of three distinct supramolecular forces.

Molecular tectonics: ribbon type coordination networks based on porphyrins bearing two pyridine or two pyridine N-oxide units

Upon combining porphyrin based tectons bearing at the 5,10 meso positions either two pyridine or two pyridine N-oxide groups, with Cd2+ or Cu2+, four ribbon-type 1-D networks were obtained and structurally characterised in the crystalline phase by X-ray diffraction methods. Although, based on tecton’s structural features, the formation of ribbon-type architectures could be anticipated, their deformation, resulting from the geometry of the connecting metal centres as well as the packing forces in the solid state, could not be predicted.

Porphyrin based metallamacrocycles

Upon combining 5,10-dipyridyl-15,20-diphenylporphyrin 1 or its copper metallated complex 2 with metal halides (MX2: M = Zn, Cd, Hg; X = I or Br) five [2 + 2] metallamacrocycles of the square type were obtained and structurally characterised in the crystalline phase by X-ray diffraction methods. Whereas the free porphyrin 1 leads to the formation of homobinuclear metallamacrocycles with both CdI2 and HgI2, a homotetranuclear metallamacrocycle resulting from the metallation of the porphyrin core is obtained in the presence of ZnI2. When using the premetallated copper complex 2, two heterotetranuclear metallamacrocycles are generated in the presence of CdI2 and HgBr2.

Chloroiron meso-triphenylcorrolates: electronic ground state and spin delocalization

Abstract Four chloroiron meso -triphenyl-substituted corrolates have been synthesized and studied by 1 H NMR spectroscopy. As in the case of the β-pyrrole-octaalkylcorrolatoiron chloride complexes studied previously [Inorg. Chem. 39 (2000) 3466], these complexes were also found to be S=3/2 Fe(III) corrolate( 2− ) π-cation radical species, where the macrocycle radical electron is antiferromagnetically coupled to the metal electrons to give an overall S=1 complex. This conclusion is based upon the large alternating-sign contact shifts observed for the meso -phenyl protons. The 1 H isotropic shifts of the pyrrole-H of these chloroiron–triphenylcorrolate complexes are similar to those of the chloroiron tri-(pentafluorophenyl)corrolate complex reported previously and said to be a S=1 Fe(IV) complex bound to a simple corrolate( 3− ) ligand [Inorg. Chem. 39 (2000) 2704]. The 19 F NMR spectrum of the latter complex shows that it has small (negative) phenyl-F isotropic shifts for all phenyl-F, which might suggest that this single compound has a different electronic structure than all other chloroiron corrolates investigated thus far. However, there have as yet been very few NMR investigations of paramagnetic metal macrocycles having fluorine substituents, and thus it is premature to conclude that the small phenyl-F isotropic shifts are definitive proof of small spin density at the meso positions of the corrolate ring. It is concluded that pyrrole-H chemical shifts alone cannot differentiate the two possible electron configurations, simple S=1 Fe(IV) (Corr 3− ) and antiferromagnetically coupled S=3/2 Fe(III) (Corr 2− ), and that based on the 1 H investigations reported in this and two previous papers, all chloroiron corrolates reported thus far, with the exception of one, have the electron configuration S=3/2 Fe(III) (Corr 2− ), in which the corrolate unpaired electron is antiferromagnetically coupled to the three metal electrons, yielding an overall spin for the complex, S=1. The electron configuration of the one exception, the strongly electron-withdrawing tri-(pentafluorophenyl)corrolate complex of iron chloride, cannot as yet be definitively assigned.

Nanopatterning of Surfaces with Monometallic and Heterobimetallic 1D Coordination Polymers: A Molecular Tectonics Approach at the Solid/Liquid Interface

The self-assembly of multiple molecular components into complex supramolecular architectures is ubiquitous in nature and constitutes one of the most powerful strategies to fabricate multifunctional nanomaterials making use of the bottom-up approach. When spatial confinement in two dimensions on a solid substrate is employed, this approach can be exploited to generate periodically ordered structures from suitably designed molecular tectons. In this study we demonstrate that physisorbed directional periodic arrays of monometallic or heterobimetallic coordination polymers can be generated on a highly oriented pyrolitic graphite surface by combinations of a suitably designed directional organic tecton or metallatecton based on a porphyrin or nickel(II) metalloporphyrin backbone bearing both a pyridyl unit and a terpyridyl unit acting as coordinating sites for CoCl2. The periodic architectures were visualized at the solid/liquid interface with a submolecular resolution by scanning tunneling microscopy and corroborated by combined density functional and time-dependent density functional theory calculations. The capacity to nanopattern the surface for the first time with two distinct metallic centers exhibiting different electronic and optical properties is a key step toward the bottom-up construction of robust multicomponent and, thus, multifunctional molecular nanostructures and nanodevices.

Molecular tectonics: coordination networks based on porphyrins bearing pyridine N-oxide groups as coordinating sites

The combination of the two positional isomers 1 and 2, porphyrin backbones bearing two pyridine N-oxide groups (PNO), with Zn(II) cations leads to 1-Zn and 2-Zn self-complementary tectons which generate in the crystalline phase analogous 1-D zigzag type coordination networks with different metrics. In both cases, only one PNO group bridges the consecutive tecton through coordination to the Zn atom which adopts the square based pyramidal geometry.

Design, synthesis, structural analysis and atropoisomerisation studies of polynucleating ligands based on porphyrins bearing catechol units

New polynucleating ligands based on a combination of a meso-tetrakis(phenyl)porphyrin core and four catecholamido units connected at the ortho positions of the phenyl moieties have been prepared. All four atropoisomers of the methoxy-protected meso-tetrakis(o-catecholamidophenyl)porphyrin 2 were obtained in high yields, however, the separation of isomers, although achievable, was found to be extremely tedious and did not allow the preparation of large quantities of the different atropoisomers. This difficulty was overcome by first separating the atropoisomers of the precursor meso-tetrakis(o-aminophenyl)porphyrin 3 and then by a quantitative condensation reaction of the separated isomers with the acyl chloride derivative of methyl-protected catechol 6. All four atropoisomers were subsequently deprotected in quantitative yields using BBr3. Although following this route the protected 2α4 and 2α3β atropoisomers were obtained on the gram scale, for the other two 2αβαβ and 2α2β2 isomers, due to separation difficulties, only low quantities could be synthesised. After a systematic kinetic study of the atropoisomerisation process, the 2αβαβ isomer was obtained in large quantities by thermal isomerisation of the random mixture of isomers of 2 in toluene at 110 °C in the presence of a large excess of trifluoroacetic acid, whereas the 2α2β2 isomer was isolated under the same conditions but in the absence of acid. All four atropoisomers were characterised by classical 1- and 2-D NMR spectroscopy. Furthermore, the 1αβαβ, 1α4, 2αβαβ, 2α4 and 3αβαβ atropoisomers were also characterised in the solid state by X-ray diffraction on single crystals.