Synthesis, structures, optical properties, and TD-DFT studies of donor-π-conjugated dipicolinic acid/ester/amide ligands

A series of 2,6- and 4-functionalized dipicolinic acid, ester, or amide featuring π-conjugated substituents such as donor-(phenyl or fluorenyl)-acetylene groups have been synthesized. Four crystallographic structures are reported. The influence of the substituent position, the nature of the donor group, and the conjugated backbone as well as the role of the pyridinic side arms on the absorption and emission properties are studied and discussed on the basis of TD-DFT calculations.