Chromophore-labelled, luminescent platinum complexes: syntheses, structures, and spectroscopic properties.

Ligands based upon 4-carboxamide-2-phenylquinoline derivatives have been synthesised with solubilising octyl hydrocarbon chains and tethered aromatic chromophores to give naphthyl (), anthracenyl () and pyrenyl () ligand variants, together with a non-chromophoric analogue () for comparison. (1)H NMR spectroscopic studies of the ligands showed that two non-interchangeable isomers exist for and while only one isomer exists for and . Supporting DFT calculations on suggest that the two isomers may be closely isoenergetic with a relatively high barrier to exchange of ca. 100 kJ mol(-1). These new ligands were cyclometalated with Pt(ii) to give complexes [Pt()(acac)] (acac = acetylacetonate). The spectroscopically characterised complexes were studied using multinuclear NMR spectroscopy including (195)Pt{(1)H} NMR studies which revealed δPtca. -2785 ppm for [Pt()(acac)]. X-ray crystallographic studies were undertaken on [Pt()(acac)] and [Pt()(acac)], each showing the weakly distorted square planar geometry at Pt(ii); the structure of [Pt()(acac)] showed evidence for intermolecular Pt-Pt interactions. The UV-vis. absorption studies show that the spectral profiles for [Pt()(acac)] are a composite of the organic chromophore centred bands and a broad (1)MLCT (5d → π*) band (ca. 440 nm) associated with the complex. Luminescence studies showed that complexes [Pt()(acac)] are dual emissive with fluorescence characteristic of the tethered fluorophore and long-lived phosphorescence attributed to (3)MLCT emission. In the case of the pyrenyl derivative, [Pt()(acac)], the close energetic matching of the (3)MLCT and (3)LCpyr excited states led to an elongation of the (3)MLCT emission lifetime (τ = 42 µs) under degassed solvent conditions, suggestive of energy transfer processes between the two states.

Near-IR luminescent lanthanide complexes with 1,8-diaminoanthraquinone-based chromophoric ligands.

Three new chromophoric anthraquinone-based multidentate ligands have been synthesised in a step-wise manner from 1,8-dichloroanthraquinone. The ligands each comprise two dipicolyl amine units and react with trivalent lanthanide ions to form monometallic complexes of the form [Ln(L)](OTf)3 as indicated by MS studies and elemental analyses. Supporting DFT studies show that the monometallic species are highly favoured (>1000 kJ mol(-1)) over the formation of a 2 : 2 dimetallic congener. Both ligands and complexes absorb light efficiently (ε ∼ 10(4) M(-1) cm(-1)) in the visible part of the spectrum, with λabsca. 535-550 nm through an intramolecular charge transfer (ICT) transition localised on the substituted anthraquinone unit. In all cases the complexes show a fluorescence band at ca. 675 nm due to the ICT emitting state. The corresponding Nd(iii), Yb(iii) and Er(iii) complexes also reveal sensitised near-IR emission characteristic of each ion following excitation of the ICT visible absorption band at 535 nm.

Water soluble, cyclometalated Pt(ii)-Ln(iii) conjugates towards novel bimodal imaging agents.

Facile conjugation of a luminescent cyclometalated Pt(II) complex with a DO3A-derived Gd(III) moiety yields a hybrid species with visible luminescence and enhanced relaxivity.

Phosphorescent, Cyclometalated Cinchophen-Derived Platinum Complexes: Syntheses, Structures, and Electronic Properties.

The syntheses of nine new monometallic heteroleptic platinum complexes [Pt(L1-4)(acac)], [Pt(L1)(hmacac/hfacac)], [PtCl(L1)(py)], [Pt(L1)(8-Q)], [Pt(L1)(bpy)](PF6) (where L1 = 2-phenyl-4-ethyl-quinolinecarboxylate; L2/L3 = N-functionalization of 2-phenyl-N-aryl/alkyl-quinoline-4-carboxamides; L4 = 2-phenyl-4-quinolinecarboxylic acid (cinchophen); acac = acetylacetonato; hmacac =2,2,6,6-tetramethyl-3,5-heptanedionate; hfacac = hexafluoroacetylacetonate; py = pyridine; 8-Q = 8-quinolinato; bpy =2,2'-bipyridine) are described from precursor dimeric Pt(II) species via an intermediate DMSO adduct of the general form [PtCl(L1-4)(DMSO)]. Single crystal X-ray diffraction studies were undertaken on three complexes, [Pt(L1)(acac)], [PtCl(L1)(DMSO)], and [Pt(L1)(bpy)](PF6). The structures show that the complexes each adopt a distorted square planar geometry (most severely in the case of [Pt(L1)(bpy)](PF6)) with indications of intermolecular Pt-Pt interactions in one example. The complexes were investigated using (195)Pt{(1)H} NMR spectroscopy, revealing varied chemical shifts that were strongly dependent upon the specific coordination environment of Pt(II). Luminescence studies showed the complexes possess a phosphorescent character with tunable emission wavelengths between 605 and 641 nm and luminescent lifetimes up to ∼450 ns. Supporting TD-DFT studies provided descriptions of the HOMO and LUMO energy levels of the key complex types, confirming an MLCT contribution to the lowest energy absorption that generally correlated well with the experimental spectra. The contribution of the Pt(5d) center to the calculated HOMOs was strongly ligand dependent, whereas the LUMOs are generally localized over the quinoline component of the cyclometalated ligand.