Complexes of prodigiosin (a naturally occurring pyrrolylpyrromethene) with H+, Cl−, HCO3- and CO2: A computational study

► DFT calculations reproduce the geometry and stability of prodigiosin complexes. ► TDDFT accurately describes the spectra of prodigiosins. ► Identity of the solvent strongly influences stability of complexes. ► CO2 complexation competes with HCO3- complexation for NH containing collectors.