Selecting pyrazole-based silver complexes for efficient liquid crystal and luminescent materials

• Optimisation of the liquid crystal properties on luminescent silver-pyrazole complexes.
• Mesomorphism is enhanced or induced by the strategic use of asymmetrically substituted ligands.
• The ‘H’ molecular shape of the complexes was determinant to improve mesomorphism.

The liquid crystal and luminescent properties of two families of silver complexes (A = [Ag(L)2][NO3] and B = [Ag(L)(NO3)]) based on 3,5-alkyloxyphenyl, 3-pyridyl-5-alkyloxyphenyl and 3-alkyloxyphenyl substituted pyrazole ligands (L) were analysed on the light of the influence of factors as the stoichiometric metal to ligand ratio or the nature of the substituents on the pyrazole ring. This latter is related to the presence of the pyridine groups or the symmetrical or asymmetrical alkylokyphenyl substitution. The interest of the research was focused on determining the molecular characteristics that optimise the mesomorphic properties/structure relationship. The thermal behaviour of A revealed that an “H” molecular shape was an imperative factor to achieve the best mesomorphic properties, while the mesomorphism of B was clearly dependent on the number and/or on the symmetric or asymmetric alkyloxyphenyl substitution on the pyrazole ring. The fluorescent properties of both types of compounds were also examined and compared.

Figure optionsDownload as PowerPoint slide