High Quantum Yield Molecular Bromine Photoelimination from Mononuclear Platinum(IV) Complexes

Abstract

Pt(IV) complexes trans-Pt(PEt3)2(R)(Br)3 (R = Br, aryl and polycyclic aromatic fragments) photoeliminate molecular bromine with quantum yields as high as 82%. Photoelimination occurs both in the solid state and in solution. Calorimetry measurements and DFT calculations (PMe3 analogs) indicate endothermic and endergonic photoeliminations with free energies from 2 to 22 kcal/mol of Br2. Solution trapping experiments with high concentrations of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor to bromine elimination.

Dihydrogen Trioxide (HOOOH) Photoelimination from a Platinum(IV) Hydroperoxo-Hydroxo Complex

“…Singlet oxygen emission experiments should provide information on the involvement of singlet oxygen in these reactions. 26 On the basis of the above results and our previous results 1,12,19 with analogous complexes, the trans-Pt(IV)L 2 (R)X 3 system is proving to be a versatile platform for elimination chemistry. Other complexes that should eliminate unusual molecules are currently under investigation.…”

Bromine photoelimination from organoplatinum(IV) complexes

“…Correlating this to reaction free energies obtained from calorimetry and DFT calculations also does not show any specific trends. 30 Again the 2(Br) with a high free energy change of 21 kcal/mol shows a very high quantum yield of 59%. 30 Hence, to consider the trends with regards to one specific aspect is not sufficient.…”

“…excited state with radical bromine character was observed. 30,43 The uv-vis spectra of 2(BrNap) and 2(Phen) measured in CH 2 Cl 2 , hexane and dimethylformamide (DMF) were the same. Thus, band shifts associated with charge transfer transitions were not observed when solvent polarity was changed for the peaks in the visible region.…”

“…The bromine reaction enthalpies of the four complexes 1(Br), 1(Ph), 1(CF 3 Ph) and 1(BrNap) were determined in toluene by the Hoff group using calorimetry. 30 The gasphase DFT calculations on 1' (PMe 3 used in place of PEt 3 ) were carried out by Prof.…”

“…Based on DFT calculations (by Prof. Sharp), calorimetry measurements (by Prof. Hoff) and Xray crystal structure parameters, steric strain is revealed in platinum(IV) complexes. 23,28,30 Correspondingly in the square planar platinum(II) complexes these effects are absent.…”