Optic nonlinearities of a copper complex of pyrazinoporphyrazine

For the copper complex of pyrazinoporphyrazine AzaPhcCu(C(CH3)(3))(8) in CH 2Cl2, we use nanosecond pulses to measure its third-order nonlinear optic e ffects at 532 nm. The results show that its effective third-order nonlinear refractive index n(2)(eff) (-7.85 x 10(-10) esu) is larger than that of th e AzaPhcCu(C12H25)(4) and the CuPc(OC5H11)(8). The reverse saturable absorp tion (RSA) of AzaPhcCu-(C(CH3)(3))(8) is demonstrated by the ratio of effec tive excited state to ground state absorption cross sections. The observed intersystem crossing lifetime tau(isc) of AzaPhcCu(C(CH3)(3))(8) (similar t o 15 ns) and AzaPhcCu(C12H25)(4) (similar to 45 ns) are longer than that of CuPc(OC5H11)(8) (similar to 5.0 ns). The aza-substituents are suggested to form a S-1(n, pi*) state as their lowest excited singlet-states, and their radiationless intersystem crossing rates (1/tau(isc)) are discussed with t he spin-orbit coupling [psi(S)|\H-SO\psi(T)] and the vibronic coupling [chi (S)|chi(T)] effects between S-1 and T-1 states.