Florina Dumitru

Self-sorting of metallosupramolecular DCLs via double-level exchange: amplification in solution and solid state modulation

Interexchanging metallosupramolecular double level imine/ligand Dynamic Constitutional Libraries (DCLs), produce, in solution, the amplification of heteroleptic complexes, which convert into homoleptic complexes via constitutional crystallization.

Columnar Self-Assemblies of Triarylamines as Scaffolds for Artificial Biomimetic Channels for Ion and for Water Transport

Triarylamine molecules appended with crown-ethers or carboxylic moieties form self-assembled supramolecular channels within lipid bilayers. Fluorescence assays and voltage clamp studies reveal that the self-assemblies incorporating the crown ethers work as single channels for the selective transport of K+ or Rb+. The X-ray crystallographic structures confirm the mutual columnar self-assembly of triarylamines and crown-ethers. The dimensional fit of K+ cations within the 18-crown-6 leads to a partial dehydration and to the formation of alternating K+ cation-water wires within the channel. This original type of organization may be regarded as a biomimetic alternative of columnar K+-water wires observed for the natural KcsA channel. Supramolecular columnar arrangement was also shown for the triarylamine-carboxylic acid conjugate. In this latter case, stopped-flow light scattering analysis reveals the transport of water across lipid bilayer membranes with a relative water permeability as high as 17 μm s-1.

New "pyrene box" cages for adaptive guest conformations.

The possibility of controlling the compression extent and the coiling shape of the 1,12-diammoniumdodecane guest is shown by changing the dimensions of the internal space of the host guanidinium 1,3,5,8 pyrene-tetrasulfonate PTS(4-) crystalline capsules by using guanidinium (G(+)), amino-guanidinium (AG(+)), and diaminoguanidinium (A2G(+)) cations.

Weak intermolecular hydrogen and halogen interactions in an isomorphous halogen series of pseudoterpyridine ZnII complexes

The synthesis and characterization of a series of halogen-substituted pseudoterpyridine ZnII homoleptic mononuclear complexes, based on ligands L11–L44 [2,6-pyridinedicarboxaldehydebis(p-R-phenylimines), R = F, Cl, Br, I] are reported. Neither of the structures contain relatively strong classical hydrogen bonds (OH⋯O, NH⋯O, OH⋯N, NH⋯N) and the structure packing is thus determined by a subtle interplay of weaker interactions. Isostructurality of the four halogen analogues is very rare, and in this study —Br, —Cl and —F are found to be isostructural in different degrees, whereas —I is not. Interestingly, although it is closely isostructural to the —Cl and —Br compounds, the F analogue is shown not to form F⋯O bonds, while the Cl and the Br analogues do form Hal⋯O bonds. This raises an important question on the role of Hal⋯O bonds in the structuration of the crystal packing, particularly the stabilization effect. Similarly, while the CH⋯Hal interaction seems to give one-dimensional cohesion in the —Cl and —Br analogues, this feature is absent in the —F analogue, despite its close isostructurality. CH⋯O interactions appear to dominate to a first degree the cohesion between the anionic trifluoromethanesulfonate network and the cationic Zn-pyridinedicarboxaldehydebis(p-R-phenylxadimines) network. The analysis of these interactions is corroborated by reduced density gradient calculations based on promolecular densities.

Exclusive Hydrophobic Self-Assembly of Adaptive Solid-State Networks of Octasubstituted 9,9'-Spirobifluorenes

An easy and powerful access to 3,3,6,6-tetrasubstituted 9,9-spirobifluorene derivatives with tetrahedral orientation of the peripheral groups (i.e., -I, -CN, -NO2, -CH═O, -COOH, -C≡CH, -4-Py) was developed. The NMR and HRMS results are in agreement with the proposed formula and the solid-state molecular structures obtained by single-crystal X-ray diffraction. They form molecular solids self-assembled via exclusive hydrophobic interactions. Solid-state selection and adaptation can be obtained on the basis of variable compact packing of functional groups present on the 9,9-spirobifluorene backbone.

Mesomeric metallosupramolecular grid architectures

We describe herein the self-assembly processes as well as the structural properties of metallosupramolecular grid-architectures, involving bis-bidentate ligand 1, based on imino-pyridine complexation subunits and tetrahedrally (Cu+, Ag+) and octahedrally (Co2+, Zn2+, Fe2+) coordinated metal ions. The NMR, electrospray ionisation mass spectrometry data and X-ray crystal structure results suggest that in solution corner- and grid-type compounds are present, while in the solid state they adopt very compact and stable [2 × 2] grids arrays. Despite the variable binding behaviours of tetrahedrally coordinated cations (Cu+, Ag+) and the four coordination (lower) number of octahedrally coordinated cations (Co2+, Zn2+, Fe2+), the flexibility of the ligand 1 induce a perfect arrangement of these components, resulting in the formation of metallosupramolecular grids. Examination of such structures suggests that simple conformational rotation around the central phenyl of ligand 1 results in the self-assembly of chiral ligands. This allows the formation of mesomeric grid-type superstructures containing an inversion centre with half-superior and -inferior inner surfaces of opposite chirality.