Highly efficient phosphorescence from cyclometallated iridium(III) compounds: Improved syntheses of picolinate complexes and quantum chemical studies of their electronic structures

The crystal structure of 5-(tri-fluoro-meth-yl)picolinic acid monohydrate reveals a water-bridged hydrogen-bonding network

The title compound [systematic name: 5-(tri-fluoro-meth-yl)pyridine-2-carb-oxy-lic acid monohydrate], C7H4F3NO2·H2O, is the acid hydrate of a pyridine with a carb-oxy-lic acid group and a tri-fluoro-methyl substituent situated para to one another on the aromatic ring. The mol-ecule forms a centrosymmetric water-bridged hydrogen-bonding dimer with graph-set notation R 4 4 (12). Hydrogen-bonding distances of 2.5219 (11) and 2.8213 (11) Å are observed between the donor carb-oxy-lic acid and the bridging water acceptor, and the donor water and carbonyl oxygen acceptor, respectively. The dimers are further linked into a two-dimensional sheet via two longer inter-molecular hydrogen-bonding inter-actions between the second hydrogen atom on the bridging water mol-ecule and both a pyridine nitro-gen atom and carbonyl oxygen with distances of 3.1769 (11) and 2.8455 (11) Å, respectively. The tri-fluoro-methyl groups extend out the faces of the sheet providing for F⋯F and C-H⋯F contacts between the sheets, completing the three-dimensional packing.