Ability of platinum(II) complexes of 2,2′-bipyridine and 1,10-phenanthroline with halides and pseudo-halides to photosensitize the production of 1O2

Synthesis and Analysis of the Structure, Diffusion and Cytotoxicity of Heterocyclic Platinum(IV) Complexes

“…The weaker features at 320 and 390 nm were tentatively assigned to metal-to-ligand charge-transfer (MLCT) transitions. The analysisb yM ackay et al [20b] using time-dependent density functionalt heory (TD-DFT) calculations indicated that their computed spectra were in agreement with the data of Shukla et al [24] The situation is different for the platinum(IV) complexes,a nd the superficial similaritiesw ith the phen spectrum may conceal some significant differences in the nature of the electronic transitions. In their computational analysiso f as eries of complexes of platinum(IV) with phena nd the azido and acetato ligands, Mackay et al [20b] found substantial differences in the unoccupied orbitals of the platinum(II) and platinum(IV) complexes (LUMO and LUMO + 1) and concluded that the prominentU Vb and at 272 nm is of mixed character for the platinum(IV) complexes, with phen playing am arginal role, and the longer-wavelength bands are attributable to LMCT transitions involving the acetato ligands, and LMCT and ligandto-ligandc harge-transfer states (LLCT) transitions involving the azido ligands.…”

“…[25] The phen spectra in dichloromethane are dominated by strong bands at 229 and 271 nm (protonated)a nd 231 and 264 nm (neutral), with some weaker structured absorption to longer wavelengths. The similarities for the longerw avelengthsa re exploredm ore fully by Shukla et al, [24] who reported the band maximaf or as eries of platinum(II) complexes of the form [Pt(phen)X 2 ]( X= Cl À ,B r À ,I À ,S CN À ,C N À ,N 3 À ), following earlier work by Rossiello [26] on comparable complexes with chloride and perchlorate as additional ligands. Thes trong bands at about 270 nm, and the weaker features (sometimes shoulders) between 350 and 370 nm, are attributed to ligand-centred absorptionb ands associated with phen p* !…”

“…These assignmentsh elp to justify the different appearances of the CD spectra,w ithoutp roviding ad etailed explanation of the band assignments.A tw avelengths shorter than 250 nm the CD spectra track the corresponding UV bands for both 1 and 1' (Figure 3). For both complexes the CD is relatively weak and negative for the strong UV absorption centred on 270 nm, notwithstanding the different orbitalc haracter suggested by Mackay et al [20b] The platinum(IV) complex (1') shows little CD activity above 280 nm, but the platinum(II) complex (1)s hows aw eak positive CD band between 325 and 360 nm, aligning with the first UV band system,p ossiblya ttributable to the phen ligand and weak negative CD below 325 nm, possibly associated with the shoulder in the UV spectrum which Shukla et al [24] suggest may be MLCT in character.…”

“…The UV absorption andC Ds pectra of the complexes 1 and 1', are shown in Figure 3, andband maximafor the family of complexesa re reported in Ta ble 4. The UV spectra are similart o the phen complexes of the two oxidation states of platinum with other ligands, [24] which have been analysed qualitatively and with the aid of TD-DFTcalculations. [20b] Although there are similarities between the UV spectra,e specially at longerw avelengths, the CD spectra are markedly different, presumably due to the differences in electronic transitions for the different oxidation states of platinum, as discussed below.…”

Fractional dependence of the free energy of activation on the driving force of charge transfer in the quenching of the excited states of substituted phenanthroline homoleptic ruthenium(ii) complexes in aqueous medium

“…1–7 The majority of the coordination compound studies focused on ruthenium( ii ) polypyridyl complexes. 36–50 Singlet oxygen photosensitized by other metal complexes such as chromium( iii ), 51–56 lanthanide complexes of metallotexaphyrin derivatives, 57 and divalent metal complexes of Pt, Mg, Cu, Ni, Ag, Cd, Co, Pd and Zn, 58 palladium and platinum complexes, 59–63 thiolato Au( i ) complexes, 64 organoiridium( iii ) 65 was also reported. Recent studies have shown that osmium( ii ) terpyridyl derivatives 66 are effective singlet oxygen photosensitizers used for photodynamic therapy.…”