Synthesis and characterization of luminescent zinc(II) complexes with a N,N-bidentate 1-pyridylimidazo[1,5-a]pyridine ligand

Ligand 2-(1-(pyridin-2-yl)imidazo[1,5-a]pyridin-3-yl)phenol (L) has been reacted in a 2:1 molar ratio
with different Zn(Y)2nH2O salts, where Y represents a polyatomic anion (Y = ClO4
, NO3
, BF4
, PF6
). The
X-ray structural analysis performed on two of the derivatives obtained, namely [Zn(L)2(ClO4)](ClO4) H2O
(1) and [Zn(L)2(CH3CN)2](BF4)2 (6), proves that as expected ligand L binds in a N,N-bidentate mode via the
pyridine ring (Npy) and the pyridine-like nitrogen of the imidazo[1,5-a]pyridine skeleton (Nim). A spectroscopic
investigation (including infrared, elemental analysis, 1H and 31P NMR, thermogravimetric analysis)
has been performed on these species, allowing complete characterizations. A preliminary survey on their
photophysical properties in the solid state was carried out: the complexes showing intense luminescence
when excited with UV light (kexc = 421–469 nm) with kmax of emission in the blue-green range (468–
500 nm) and moderate absolute photoluminescence quantum yields (PLQYs)