Silver pyrazolates with columnar liquid‐crystal phases that are stable at room temperature have been prepared by reaction of silver nitrate with 3,5‐diarylpyrazolates. The complexes consist of open‐chain oligomers, despite the fact that the most common structural type for homoleptic coinage metal pyrazolates is the trimeric metallacycle [M(μ‐pz)]3. The special characteristics of silver in forming reversible metal–ligand bonds in solution, evidenced experimentally, leads to supramolecular organizations in which the silver cations promote self‐organization of the nonmesomorphic pyrazolates into helical 1D polymers that exhibit columnar mesophases. The materials are readily soluble in common organic solvents and are liquid‐crystalline over a broader temperature range than their gold counterparts, which are known to form discrete cyclic trinuclear species. Thin films of the silver complexes show luminescence at room temperature. The compounds described here are the first examples of luminescent metallomesogens formed by a main‐chain coordination polymer.

Several new cis-[RhCl(CO)2(Ln)] complexes have been prepared using different polycatenar pyrazole ligands (Ln) in order to obtain columnar liquid crystalline arrangements. The topology of the ligand plays an essential role, and a mesophase is induced at room temperature from a nonmesogenic pyrazole only when it is symmetrically substituted with six decyloxy chains. The single-crystal structure of a methoxy-substituted analogue, 3,5-bis(3,4,5-trimethoxyphenyl)pyrazole, is formed by globular tetrameric structures held together by H-bonding. However, parallel dimers are present in the corresponding cis-chlorodicarbonylrhodium(I) complex, a situation that explains the induction of a columnar mesophase in the decyloxy-substituted complex. The XRD pattern of the mesophase is consistent with a hexagonal symmetry in which the columns are formed by molecules assembled in an antiparallel mode. The crystal-to-mesophase transition was also detected by spectroscopic techniques as a shift in the IR carbonyl stretching bands and the appearance of a charge-transfer band in the absorption spectrum with thermochromic behavior.