Photoluminescence of tris(pyrazolyl)hydridoborato thallium(I) complexes

The coordination compounds TlTp3−R with Tp3−R=hydridotris-(3-R-pyrazolyl-1-yl)-borate anion (R=tert-butyl, phenyl, 2-thienyl and p-tolyl) show a photoluminescence which originates from the metal-centered sp triplet of the Tl+ ion. In the solid state, the emission wavelength depends on the substituent R. Since the Tl+…Tl+ distance varies with R the emission energy seems to reflect the extent of metal–metal interaction in the excited state.