Smallest Optical Gap for Pt(II)-Pt(IV) Mixed-Valence Pt-Cl and Pt-Br Chain Complexes Achieved by Using a Multiple-Hydrogen-Bond Approach.

A multiple-hydrogen-bond approach was applied to shorten Pt-X-Pt distances in Cl- and Br-bridged Pt chain complexes. [Pt(dabdOH)2Cl]Cl2 (5) and [Pt(dabdOH)2Br]Br2 (6) (dabdOH = (2 S,3 S)-2,3-diaminobutane-1,4-diol) contain hydroxy groups, which form additional hydrogen bonds with counteranions. 5 has the shortest Pt-Cl-Pt distance (5.0747(8) Å) of all Cl-bridged Pt chain complexes reported to date. Furthermore, the smallest optical gap (1.45 eV for 5 and 1.19 eV for 6) in any Cl- or Br-bridged Pt chain complex was achieved. 6 has the highest electrical conductivity (1.9 × 10-5 S cm-1 at room temperature) of all Br-bridged Pt chain complexes. This study shows that the introduction of additional hydrogen bonds between the ligands and halides is effective to enhance the electronic properties of halogen-bridged metal complexes.