Abstract

A series of new two-photon pumped (TPP) up-conversion lasing dyes, named as CSPI, DPASPI, PSPI, DEASPI and HEASPI respectively, have been synthesized. These dyes are stilbene-type chromophores end-capped with the same acceptor group but with varied donor groups, whose different electron-donating abilities can be ordered by ¹H NMR chemical shift data. PM3 calculations show that attaching different donors changes the bond length alternation (BLA) and charge density distribution of the styrylpyridine skeleton. These chromophores exhibit different two-photon up-conversion emission behavior. Pumped by a 1064 nm, ∼40 ps mode-locked Nd ∶ YAG laser pulses, all chromophores showed two-photon pumped (TPP) up-conversion laser emission, but the efficiencies showed a difference of about two orders of magnitude, ranging from an up-conversion efficiency of 10.7% for DEASPI to 0.13% for CSPI under the same experimental conditions. The results show that the efficiency of two-photon pumped emission is related to the intramolecular charge transfer character of the chromophore. The two-photon pumped lasing efficiency increases both with decreasing BLA and with increasing intramolecular charge transfer character, measured by the parameter Δρ_1,2.