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International audience; Three room-temperature metallomesogens based on Zn(II) cations pentacoordinated by different chelating N^N^N terpyridines and two monodentate gallate co-ligands were designed and synthesized. Depending on the terpyridine ligand's tip functionality, the complexes self-assemble into either a 3D hexagonal mesophase or into a columnar hexagonal mesophase. A systematic study between the structure (molecular architecture, arrangement of the molecules and columns, and chains in both types of mesophases) and photophysical properties (emission maxima and yields, lifetimes of the excited states in the mesophase), correlated with investigations of single molecules in solution, was conducted. Remarkably, one complex exhibited a record quantum yield of 95.0% in solution, while in the mesophase, despite quenching due to the radiative deactivation from the ILCT state, still retained a considerable emission yield of ϕ = 20.2%. The polarized emission of an oriented film, determined for the first time in columnar metallomesogens, shows a dichroic emission ratio (I||/I⊥) of 1.30. DFT and TDDFT computational studies confirmed the origin of the observed fluorescence anisotropy from the transition dipole moment oriented along the C2 symmetry axis of the molecule combined with a high level of order in the 3D mesophase.

A new synthetic approach for homo- and heteronuclear complexes, based on N,N′-bis[(3-methoxysalicylideneamino)-propyl]-piperazine (H2L) Schiff-base ligand, has been developed. The ligand has been crystallized in the form H2L·2DMSO and its structure has been solved. Using this ligand, the following complexes have been synthesized: [CoL](ClO4) (1), [Zn2L(CH3COO)2]·2H2O (2), [Cu3L2(NO3)2] (3) and [LaCu6L4(H2O)2(NO3)2](NO3)5·15H2O (4). The 1–4 complexes were characterized by elemental analysis, X-ray crystallography, infrared and diffuse reflectance spectroscopy. The crystallographic investigations revealed that H2L presents the stable chair conformation of the piperazine ring, while its coordination mode changes according to the nature of the metal ion and counterion, respectively, allowing the formation of mono- (1) and oligonuclear (2–4) complexes. Compound 1 consists of a mononuclear complex cation, where the double-deprotonated ligand (L2−) encapsulates the trivalent cobalt ion. In compound 2, L2− acts as a symmetrical binucleatig ligand through the two N2O sets disposed on each side of the piperazine ring and coordinates two zinc(II) ions. Compounds 3 and 4 contain trinuclear units where two ligand molecules coordinate unsymmetrically three CuII ions, with the N3O donor set wrapped around the peripheral CuII and the remaining NO sets bound to the central CuII ion. Two such trinuclear moieties coordinate the LaIII ion in crystal 4. Electrochemical behavior of compounds 1 and 3 and luminescent properties of compound 2 are discussed.