Luminescence properties and crystal structure of two metal 8-hydroxyquinoline complexes at high pressure

The fluorescence emission and X-ray diffraction of two metal (Ca2+ and Zn2+) 8-hydroxyquinoline complexes (Caq(2) and Znq(2)) have been measured at high pressure. It has been found that pressure can influence the emission dramatically. With increase of pressure Caq(2) gives increasing of its emission within 3 GPa and drops quickly when the pressure gets higher. At about 7 GPa it shows almost no emission at all. The emission of Znq(2) decreases gradually with increase of the pressure. The emission intensity is about 10% of its original when the pressure gets 7 GPa. The result of in situ X-ray diffraction of Caq(2) indicates that at about 3 similar to 4 GPa it starts a phase transition to amorphous and this transition completes at 7 GPa. All of the diffraction peaks has disappeared at this pressure. Znq(2), however, gives no significant phase transition up to 16 GPa according to its in situ X-ray diffraction result at pressure.