Benzothiazole‐Based Cycloplatinated Chromophores: Synthetic, Optical, and Biological Studies. Issue 10 (25th January 2018)

• Record Type: Journal Article
• Authors: Lalinde, Elena; Lara, Rebeca; López, Icíar P.; Moreno, M. Teresa; Alfaro‐Arnedo, Elvira; Pichel, José G.; Piñeiro‐Hermida, Sergio
• Is Part Of: Chemistry. Volume 24:Issue 10(2018)
• Page Start: 2440
• Page End: 2456
• Publication Date: 2018-01-25
• Subjects: cell imaging -- cytotoxicity -- luminescence -- platinum -- protonation; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201705267
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Cycloplatinated complexes based on 2‐(4‐substituted)benzothiazole ligands of type [Pt(R‐PBT‐κ C, N )Cl(L)] (PBT=2‐phenylbenzothiazole; R=Br (1 ), Me2 N (2 ); L=dimethyl sulfoxide (DMSO;a ), 1, 3, 5‐ triaza‐7‐phosphaadamantane (PTA;b ), triphenylphosphine 3, 3′, 3′′‐trisulfonate (TPPTS;c )) and [Pt(Br‐PBT‐κ C )Cl(PTA)2 ] (3 ) are presented. On the basis of the photophysical data and time‐dependent (TD)‐DFT calculations (1 a and2 a ), the low‐lying transitions (absorption and emission) were associated with ligand‐center (LC) charge transfer, with minor metal‐to‐ligand charge transfer (MLCT), and intraligand charge transfer (ILCT) [Me2 N‐PBT→PBT] excited states, respectively. Simultaneous fluorescence/phosphorescence bands were found in fluid solutions (and also in the solid state for2 a ), which become dominated by triplet emission bands in rigid media at 77 K. The effect of the concentration on emissive behavior of2 a, b indicated the occurrence of aggregation‐induced luminescence properties related to the occurrence of metal–metal and π⋅⋅⋅π interactions, which are more enhanced in2 a because of the less bulky DMSO ligand. The behavior of2 a toward para ‐toluenesulfonic acid (PTSA) in aerated acetonitrile and to hydrogen chloride gas in the solid state has been evaluated, thus showing a clear reversible change between the 1 ILCT and 3 LC/ 3 MLCT states due to protonation of the NMe2 group (theoretical calculations on2 a‐H + ). Solid2 a undergoes a surprising oxidation of the Pt II center to Pt IV with concomitant deoxygenation of DMSO, under prolonged reaction with hydrogen chloride gas to afford the Pt IV /dimethyl sulfide complex ( mer ‐[Pt(Me2 N‐PBT‐ κC, N )Cl3 (SMe2 )]; mer ‐4 ), which evolves in solution to fac ‐4, as confirmed by X‐ray studies. Cytotoxic activity studies on A549 and HeLa cell lines indicated cytotoxic activity of1 b and2 a, b . In addition, fluorescent cell microscopy revealed cytoplasmic staining, more visible in perinuclear areas. Inhibition of tubulin polymerization by1 b in both cells is presented as a preliminary mechanism of its cytotoxic action. Abstract : Benzothiazole on Pt : The optical properties and biological activities of two series of cycloplatinated complexes featuring 2‐arylbenzothiazole are presented. A complex series of reactions of [Pt(Me2 N‐PBT)Cl(DMSO)] (DMSO=dimethyl sulfoxide, PBT=2‐phenylbenzothiazole) with hydrogen chloride gas in the solid state results in the unexpected formation of a Pt IV /dimethyl sulfide complex. Inhibition of tubulin polymerization by1 b is presented as a preliminary mechanism of their cytotoxicity (see picture; PTA=1, 3, 5‐triaza‐7‐phosphaadamantane, TPPTS=triphenylphosphine 3, 3′, 3′′‐trisulfonate).