Effects of Mn doping on (TiO2)n (n = 2–5) complexes

Mn-doped TiO2 systems are of interest for low cost and high efficiency photocatalysts. However, little is known about the effects of doping on their structure. In this work, Mn is doped into (TiO2)n (n = 2–5) complexes. In the most stable structures of Mn doped TiO2 complexes, the overall appearance of the cluster does not change much from that of the associated parent complex. Mn–O bonds are usually shorter, and nearby Ti–O bonds lengthen slightly. However, the angle centered on Mn significantly increases. Structures exhibit trigonal planar arrangements around Mn with 3 O ligands and tetrahedral arrangements with four ligands. The most stable structures typically have Mn at lower coordinated positions. Relative to the parent TiO2 systems, occasionally a Mn–O bond breaks in order to maintain a low coordination number of Mn. The HOMO–LUMO gap decreases significantly by Mn doping, but this decrease is not proportional to the number of doped Mn.