Synthesis, crystal structure and green luminescence of a novel manganese(II)-based hybrid: bis[( tert -butoxycarbonyl)methyltriphenylphosphonium] tetrachloridomanganate(II)

The title novel phosphonium-based manganese(II) hybrid crystal, {(C 24 H 26 O 2 P) 2 [MnCl 4 ]} n or (TBTP) 2 [MnCl 4 ], was synthesized via slow evaporation. Single-crystal X-ray diffraction reveals that it crystallizes in the monoclinic space group P 2 1 / n , featuring discrete slightly distorted tetrahedral [MnCl 4 ] 2− anions and bulky (TBTP) + cations [(TBTP) + is ( tert -butoxycarbonyl)methyltriphenylphosphonium] with weak C—H...Cl interactions. The material exhibits green luminescence centred at 515 nm with a millisecond-scale lifetime (2.83 ms), which is unequivocally assigned to the long-lived spin-forbidden Mn 2+ 4 T 1 → 6 A 1 d – d transition. Electronic structure calculations reveal a direct band gap (with the noted underestimation typical of the PBE functional) and, more importantly, a clear spatial separation of the frontier orbitals between the inorganic and organic components. This orbital separation, likely aiding in the isolation of the luminescent [MnCl 4 ] 2− centres, is consistent with the observed long emission lifetime. This work enriches the family of phosphonium-based hybrid metal halides and provides insights into the structure–property relationships governing Mn 2+ emission in such systems.