Isostructural coordination chains assembled with aminopyrazine: Decreasing photoluminescence yield by Cd(II) replacement for Mn(II)

Abstract A cadmium coordination polymer assembled with aminopyrazine (ampyz) and acetate (AcO) was recently found to be a high-efficiency material able to convert ultraviolet radiation into blue light, with internal and external photoluminescence quantum yields (iPLQY and ePLQY) approaching 80%. Here we were inspired to prepare a blue-light-emitter based on its structure by replacing the toxic cadmium element for Mn2+. The isostructural Mn2+ coordination polymer was obtained and its structure was elucidated by single-crystal X-ray diffraction. Its optical properties were assessed and understood based on TD-DFT calculations. Low-gap d-shaped HOMO-LUMO orbitals were found intercalating those responsible for UV absorption. Therefore, low-frequency radiative decay occurs before the target luminescence, depleting much its blue-light-emission efficiency which doesn't achieve 3%. This novel material allowed us to conclude that the cadmium d10 closed-shell is decisive to the high-efficiency brightness of the literature compound.