A new family of Pt(ii) luminescent metallomesogens based on dicatenar pyridylpyrazolate ligands [Pt(pzR(n,n)py)2] (R(n,n) = C6H3(OCnH2n+1)2,n= 4–18) has been prepared, and their mesomorphic and photophysical properties are described.

Dicatenar pyridine-functionalised pyrazole ligands [Hpz(R(n,n)py)] (R(n,n) = C6H3(OCnH2n+1)2, n = 4, 6, 8, 10, 12, 14, 16, 18) have been strategically synthesised to be used as new building blocks for designing discotic liquid crystalline materials. Their coordination to Pd(II) fragments has allowed to achieve two novel families of metallomesogens, [Pd(pz(R(n,n)py))2] () and [PdCl2(Hpz(R(n,n)py))] (), in which the ligand is coordinated in the anionic form as pyrazolate or in the neutral form as pyrazole, respectively. Thermal studies showed that the ligands with n = 14 and 16 carbon atoms, as well as all the palladium complexes, display discotic mesophases in the temperature range of 68-141 °C. The results indicate that the coordination environment around the metal is a determining factor which allows control of the supramolecular arrangement of the mesophase. Disc-like molecules from complexes pack themselves into cylindrical structures that result in hexagonal columnar phases (Colh), while the half-disc shaped molecules from self-assemble into a layer with an antiparallel dimeric disposition which generates lamellar columnar phases (ColL). Schematic models based on X-ray powder diffraction (XRD) experiments are proposed to illustrate the molecular organisation of these Pd metallomesogens in the columnar mesophases.

Herein, we report as eries of unsymmetrical bispyrazolate-typeP t II compounds that exhibit mesomorphism at low temperatures and photophysicalm ulti-stimuli-responsive properties.T hese Pt II compounds show a great ability to be self-assembled by intermolecular Pt···Pt interactions in the solid state,s og enerating ac olumnar stackingo fm olecules that is responsible for the formation of the mesophases. By controlling the nature of the molecular assembly through external stimuli such as the temperature, the pressure, or the presenceo fv apours or solvents, it is possible to modulate the luminescence behaviour of thesem aterials.T he Pt II monomers emit ag reenish light, whereas aggregation of molecules produces ar edshifted emission. These metallomesogens also show a high stability ands uccessive grinding/fuming cycles can be performedw ithoutd egradation of the sample. The applicationo ft hese materials is very attractive as rewritable luminescent platforms, and their use is already demonstrated.Metallomesogensa re consideredsoft materials in which the establishment of intermolecular interactions and short contacts is favoured. [1] Therefore, the self-assembly of molecules will determinet he energy levelso ft he HOMOa nd LUMO orbitals, this fact openingawide range of possibilities in relationw ith the photophysical behaviour of this kind of nanomaterials. [2] It is well known that the luminescence emission in such systems can be originated from ag reat variety of excited states, such as ligand centre charge transfer (LCT), intraligand charge transfer (ILCT), metal-to-ligand charge transfer (MLCT), and metalmetal-to-ligand charget ransfer (MMLCT). [3] Here the nature of the coordinated ligands, as well as that of the counter-ions (in the case of ionic species), play ak ey role. As mall modification in the molecular structure can induce the formation of new intermolecular interactions, and this can originaten otable changes in its properties ande ven give rise to stimuli-responsive behaviours. [4] Many authors have demonstratedt he versatility of the Pt II metallomesogens to emit light in aw ide spectral range of 400-800nm, simply by introduction of ab ulky substituent group, for example;o rb ym odification of the number of terminal alkyl chains. [5] Particularly,the study of species in which the platinum centre is coordinated to delocalised p-systems is arousing speciali nterest becauset he phosphorescent nature of the emission is boosted at room temperature. [6] Materials that exhibit both liquid crystal and stimuli-responsive properties have been reported in the literature, but are very scarce. [4b,c, 7] Herein, we describe as eries of unsymmetrically four-coordinated Pt II metallomesogens bearing one pyridylpyrazolate and one isoquinolinylpyrazolate ligands, both being additionally carriers of dicatenar alkyloxyphenyl substituents. The compounds are, thus, four-chained, decorated with alkyl chain lengthsf rom four to 18 carbona toms (compounds 1-8; Scheme 1). The introductiono fa symmetryi se xpected to fa...

New dicatenar isoquinoline-functionalized pyrazoles, [Hpz(R(n,n)iq) ] (R(n,n)=C6 H3 (OCn H2n+1 )2 ; n=4, 6, 8, 10, 12, 14, 16, 18), have been strategically designed and synthesized to induce mesomorphic and luminescence properties into the corresponding bis(isoquinolinylpyrazolate)platinum(II) complexes [Pt(pz(R(n,n)iq) )2 ]. Thermal studies reveal that all platinum(II) compounds exhibit columnar mesophases over an exceptionally wide temperature range, above 300 °C in most cases. The photophysical behavior was also investigated in solution and in the solid state. As a consequence of the formation of Pt⋅⋅⋅Pt interactions, the weak greenish emission of the platinum derivatives turns bright orange in the mesophase. Additionally, the complexes are sensitive to a great variety of external inputs, such as temperature, mechanical grinding, pressure, solvents, and vapors. On this basis, they are used as dopant agents of a polyvinylpyrrolidone or poly(methyl methacrylate) polymer matrix to achieve stimuli-responsive thin films.