A convenient route to synthesize 1,2,4-triazolo[1,5-a]pyrimidine derivatives and their one and two-photon absorption spectral properties

A convenient method for synthesizing α-(1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonyl)methane derivatives, 3 and 4, by the well known Knoevenagel reaction, in one step, is described. The two chromophores are stilbene-type chromophores containing the same D-π-A structures and end-capped with aromatic group as their donors. Measured with femtosecond multipass Ti:sapphire amplifier as irradiation source (pumped by the laser at 800 nm), the two chromophores show efficient two-photon induced orange red fluorescence emission. The experimental results indicate that the numbers of branches of the two chromophores affect their one-photon properties and two-photon up-conversion emission behaviors, and with the increasing numbers of branches, their wavelengths of λabsmax, λspfmax and λtpfmax exhibit bathochromic shifts.