Ultrafast excited-state dynamics of Ni-contained covalently bonded phthalocyanine–porphyrin conjugates

• Nonlinear optical responses and excited state dynamics of titled compounds are investigated.
• Two samples exhibit SA under picosecond regime and large RSA under femtosecond regime.
• The lifetime of energy transfer process and charge transfer process are achieved.

Two covalently bonded phthalocyanine–porphyrin conjugates metalated with nickel were synthesized and spectroscopically characterized. The nonlinear optical responses and excited-state dynamics of these compounds were investigated via picosecond and femtosecond Z-scan and femtosecond pump-probe measurement, respectively. Both samples exhibited saturable absorption on picosecond regime and large reverse saturable absorption on femtosecond regime, which is attributed to the energy transfer from excited porphyrin unit to phthalocyanine ligand. The excited-state decay kinetics of both compounds were fit with a tri-exponential model with fast (∼500 fs), medium (∼10 ps), and slow (∼200 ps) components. Our results revealed the photo-physical mechanism of the metal contained covalently bonded phthalocyanine–porphyrin conjugates, demonstrating the effect of intra-molecule energy transfer process on nonlinear optical properties.