Polycatenar pyrazole and pyrazolate ligands as building blocks of new columnar Pd(ii) metallomesogensElectronic supplementary information (ESI) available: Full characterisation of the pyrazole ligands and their corresponding Pd(ii) metallomesogens, selected bond distances and angles for 1 and 12, PLUTO molecular drawing for 17 and X-ray crystallographic data in CIF format for 1 and 12. CCDC 977934 and 977935. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4

• Main Authors: Cuerva, Cristián, Campo, José A, Ovejero, Paloma, Torres, María R, Cano, Mercedes
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00369a

Dicatenar pyridine-functionalised pyrazole ligands [Hpz R( n , n )py ] (R( n , n ) = C 6 H 3 (OC n H 2 n +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 ] ( I ) and [PdCl 2 (Hpz R( n , n )py )] ( II ), 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 I pack themselves into cylindrical structures that result in hexagonal columnar phases (Col h ), while the half-disc shaped molecules from II self-assemble into a layer with an antiparallel dimeric disposition which generates lamellar columnar phases (Col L ). 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. The supramolecular organisation of discotic Pd( ii ) complexes in the mesophase can be controlled by varying the coordination environment around the metal centre.