We describe the preparation of six diketones based on the frameworks of five bis-naphthoporphyrins and one perinaphthoporphyrin. All diketones derive from meso-tetraarylporphyrins having incorporated ...two carbonyl groups, each one connected to one β-pyrrole carbon and one ortho carbon atom from a meso-aryl group. These compounds were all produced in good yield by intramolecular Friedel−Crafts acylation, either from porphyrins meso-substituted by o-carboxyphenyl or o,o ‘-dicarboxyphenyl substituents or from porphyrins bearing carboxy groups attached to the pyrrolic β-positions. Although the former reaction does not show significant regioselectivity when run on nickel complexes, the opposite is true for the corresponding free bases. All diketones show a spectacular bathochromic shift of the UV−vis absorption, the longest wavelength bands absorbing in the 700−825 nm range. Two compounds were structurally characterized by X-ray diffraction. In the case of the diketone, whose carbonyl groups are attached to vicinal pyrrolic β-positions, a significant intermolecular interaction between the two carbonyl groups and an aromatic hydrogen atom was detected.
Ligands based on oligoethyiene glycol units bearing at their extremities benzonitrile groups behave in the crystalline phase as tectons and lead in the presence of silver cation to different ...coordination networks. Depending on the number of glycol units, 1-D stair type or 1-D interdigitated and 2-D interwoven architectures composed of helical strands are obtained.
Pyridine and pyrimidine groups connected through amide functions can be combined into specific sequences that self-organize into either helical or linear structures enforced by the formation of ...intramolecular hydrogen bonds.
The synthesis and characterisation of novel chelate nitrogen ligands with phasmidic tails (pyridine-triazole ligand
1b
; 2,2′-bipyrimidine ligands
2b
and
3b
) as well as their titanium(
iv
) ...coordination complexes are reported. The analogous ligands
1a
,
2a
and
3a
with methoxy substituents instead of the tails were also synthesized, together with titanium complexes that could be crystallographically characterised. A good agreement is noticed between analytical data of the complexes in solution (NMR) and in the solid state (X-ray diffraction). The complexes are overall robust on phases like alumina or silica, so that they could be characterised by TLC and sometimes chromatographied. Supramolecular architectures were generated from an equimolar solution of titanium(
iv
) isopropoxide, ligand
1a
and a polyphenol ligand
5
-H
4
, leading to a double-stranded helicate characterised by MS, NMR and crystallography, which was then converted into a trinuclear complex as shown by MS and NMR DOSY data. The liquid-crystalline behaviour of the ligands
1b
,
2b
and
3b
incorporating the long alkyl tails and that of the complexes derived from these ligands have been investigated.
The mesogenic properties of pyridine-triazole and bipyrimidine chelates, and those of their derived robust Ti(
iv
) complexes have been investigated.
Control over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly ...connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym groups. A series of such strands of different lengths, up to ten hyz units, i.e., 1–7, were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by 1HNMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 1/3 turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyzpym) subunit a particularly attractive helicity codon.
Neutral hybrid 2-D networks have been generated using a bis-amidinium capable of chelating M(CN)6(3-) anions via hydrogen bonds: the packing of the achiral 2-D networks leads to channels which are ...occupied by water molecules forming polymeric H-bonded chains; furthermore, owing to the dihapto mode of H-bonding, the presence of supramolecular chirality of the delta' and lambda' types taking place within the second coordination sphere of the metallic centre has been demonstrated.
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