Platinum complexes luminescence

As part of a search for other ligands capable of adopting a square-planar configuration about a metal atom and thus potentially able to form stacked units our attention was drawn to the ligand H2P2052- (diphosphonate), usually abbreviated pop. Platinum complexes of this ligand - in particular [Pt2 (pop) i,] l - have already been subject to interesting studies of their luminescence, electronic, Raman and infrared spectra (12-161. Our initial objectives were to try to incorporate [Pt v(en)2X2]2+ (en =... 

Recently we observed eel of the binuclear platinum complex tetra-kis(diphosphonato)diplatinate(II) (Pt (pop) ) (37). This anion has attracted much attention due to its intense green luminescence in room temperature solution (38-40) (excited state of this complex undergoes oxidative (42) and reductive quenching (41). From the quenching experiments the redox potentials were estimated to be E° = -1.4 V vs. SCE for the reduction and E° 1 V for the oxidation of Pt2(pop) - (41). The potential difference of 2.4 V almost matches the energy of the phosphorescing triplet ( 2.5 eV) of Pt -(pop) . Consequently, it should be possible to observe eel of this... 

Mixed-ligand square-planar platinum(II) complexes of the type [Pt(L) (L Xmnt)] (15), where L = L = P(OPh)3, P(OEt)3, PPh3 L + L =l,5-cyclooctadiene (cod), l,2-bis(diphenylphosphino)methane (dppm) have also been investigated for their photoluminescent properties (59, 90, 91). These complexes luminesce in the solid state at 298 K and at 77 K in frozen solvent... 

Luminescence has been observed from a large number of later transition element complexes and a rich array of excited states have been observed. Related sections from CCC (1987) include Chapter 16.5 on Pt, Rh, and Ir complexes, 36.3 on Mo halide clusters, 43 on Re complexes, 45.4 on Ru polypyridyls, 46.4 on Os polypyridyls, 48.6 on Rh complexes, and sections of Chapter 52 on Pt complexes. Several recent reviews have been published on polynuclear complexes, the photophysics of gold complexes,and platinum diimine complexes. Many other more narrowly focused review articles have been published on transition metal complex luminescence a significant number are published in the journal Coordination Chemistry Reviews and some of these reviews are cited in this chapter. 

Alkynyl complexes contain metal-carbon bonds in which the metal is bound to the sp-hybridized carbon at the terminus of a metal-carbon triple bond. The materials properties of these complexes have been investigated extensively. The properties of these complexes include luminescence, optical nonlinearity, electrical conductivity, and liquid crystallinity. These properties derive largely from the extensive overlap of the metal orbitals with the ir-orbitals on the alkynyl ligand. The M-C bonds in alkynyl complexes appear to be considerably stronger than those in methyl, phenyl, or vinyl complexes. Alkynyl complexes are sometimes prepared from acetylide anions generated from terminal alkynes and lithium bases (e.g., method A in Equation 3.42), but the acidity of alkynyl C-H bonds, particularly after coordination of the alkyne to the transition metal, makes it possible to form alkynyl complexes from alkynes and relatively weak bases (e.g., method B in Equation 3.42). Alkynyl copper complexes are easily prepared and often used to make alkynylnickel, -palladium, or -platinum complexes by transmetallation (Equation 3.43). This reaction is a step in the preparation of Ni, Pd, or Pt alkynyl complexes from an alkyne, base, and a catalytic amoimt of Cul (Equation 3.44). This protocol for... 

Furthermore, two-photon fluorescence microscopy was used to show that a cyclometalated platinum(II)-rhodamine complex 11 can act as a selective indicator for mercury(II) ions in aqueous solution, including when incubated in cells (Fig. 11). Luminescent cyclometalated platinum complexes were also designed for potential in photodynamic therapy, with a 2-(2 thienyl)polypyridyl complex synthesised by Selke et al. displaying potent photoactivity and localisation in mitochondria and the nucleus. ... 

The luminescence decay occurs as a single exponential with a triplet state lifetime of 0.53 0.02 //s. The transient difference absorption spectrum of Pd2(dba)3 shows an intense peak at 600 nm, which decays by a double exponential process. The observed lifetimes of the two processes are 1.0 0.1 ns and 0.50 0.03 The long-lived decay corresponds to an MLCT triplet deactivation process, whereas the short-lived pathway is likely associated with an isomerization of the complexed dba, rather than with a fluorescence decay from the excited singlet state. These excited state lifetimes in the nanosecond region are much shorter than that found for the cis-trans isomerization in free dibenzylideneacetone (5.2 //s). This isomerization must therefore be occurring at a coordinated and not a free dba. For Pt2(dba)3 only a single exponential decay is observed with a lifetime of 0.26 ps. This decay is due to an MLCT triplet deactivation process. In this case no short-lived decay process is observed. This difference may be due to the increased strength or to the decreased lability of the metal-alkene bond in the zerovalent platinum complex. 

The luminescent, dinuclear platinum(II) species [Pt2(/x-S)2(dppy)4] (134) can be prepared by treating [PtCl2(dppy)2] with NaSH in the presence of NEt3 under anaerobic conditions.331 When the complex is dissolved in CH2C12 solution, pale-yellow crystals of [Pt(S2CH2)(dppy)2] (135) are formed, the first example of a four-membered, saturated dithiolato platinacycle. 

The aim of this chapter is to review the chemistry of chalcogenolates in the last 10 years. The more recent reviews in this field included chalcogenolates of the s-block elements,13,14 early transition metal thiolates,15 metal complexes with selenolate and tellurolate ligands,16 copper(I), lithium and magnesium thiolates,17 functionalized thiolate complexes,18 19 pentafluorobenzenethiolate platinum group compounds,20 tellurium derivatives,21 luminescent gold compounds,22 and complexes with lanthanide or actinide.23... 

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