Studies of the Room-Temperature Absorption and Emission Spectra of [Pt(trpy)X]+ Systems

Abstract

We report absorption and luminescence data for a series of d8 complexes with the formula [Pt(trpy)X]+ where trpy denotes 2,2':6/,2"-terpyridine and X = Cl, NCS, OMe, or OH. Each complex exhibits three or four relatively low-energy absorption maxima in the near-UV and visible regions with extinction coefficients on the order of 1000 M-1 cm-1. Since these energies are well below those of the 'ir-ir* transitions of the coordinated trpy ligand, we assign the bands as metal-to-ligand transfer (CT) transitions. At room temperature in deoxygenated acetonitrile each complex, save the chloride derivative, exhibits a broad, unstructured emission signal. The corrected emission maxima (and lifetimes) are 588 nm (3.5 ns), 654 nm (180 ns), and 621 nm (170 ns) for X = NCS, OMe, and OH, respectively. The thiocyanate and hydroxide derivatives also give stable, emissive solutions and significantly enhanced emission lifetimes in methylene chloride. The emissions are assigned to 3d-ir* CT excited states. Efficient radiationless decay via a low-lying 3d-d state may explain the fact that there is no detectable emission from the chloride derivative. To obtain additional information about these systems, we have solved the crystal structure of [Pt(trpy)OMe] (BPh4). The crystal symmetry is P\. The important lattice information includes: Z = 2, a = 10.656(2) Á, b = 11.830(5) A,c= 14.240(3) A, a = 110.47(2)°, ß = 92.52(2)°, and y = 105.62(3)°. In the final stage of refinement, R = 0.056. The coordination geometry is more-or-less rhombic with slightly shorter bonds to the methoxide oxygen and the central nitrogen of the trpy ligand.

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

“…The electronic absorption spectra of alkynylplatinum(II) terpyridine molecular rectangles 1−4 in dichloromethane solution at room temperature displayed intense intraligand [π → π*] transitions of the terpyridine and the alkynyl ligands at 250−345 nm together with the moderately intense absorptions at 420−490 nm, which are assigned as admixtures of metal-to-ligand charge transfer (MLCT) [dπ(Pt) → π*(terpyridine)] and ligand-to-ligand charge transfer (LLCT) [π(C≡CR) → π*(terpyridine)] transitions according to previous spectroscopic studies on alkynylplatinum(II) terpyridine systems (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Molecular rectangles 1−4 in degassed acetonitrile solution and solid state at 298 K exhibited structure-less emission bands at 620−700 nm, which are tentatively assigned as originated from the 3 MLCT/ 3 LLCT [dπ(Pt)/ π(C≡CR) → π*(terpyridine)] excited state with similar trends to their electronic absorptions.…”

Self-assembly of alkynylplatinum(II) terpyridine amphiphiles into nanostructures via steric control and metal–metal interactions

“…Detailed analysis of temperature-dependent UV-visible absorption spectra of the nanostructured tubular aggregates also provided insights into the assembly mechanism and showed the role of metal−metal interactions in the cooperative supramolecular polymerization of the amphiphilic platinum(II) complexes. noncovalent interactions | platinum complex | nanoaggregates S quare-planar d 8 platinum(II) polypyridine complexes have long been known to exhibit intriguing spectroscopic and luminescence properties (1-54) as well as interesting solid-state polymorphism associated with metal−metal and π−π stacking interactions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)25). Earlier work by our group showed the first example, to our knowledge, of an alkynylplatinum(II) terpyridine system [Pt(tpy)(C ≡ CR)] + that incorporates σ-donating and solubilizing alkynyl ligands together with the formation of Pt···Pt interactions to exhibit notable color changes and luminescence enhancements on solvent composition change (25) and polyelectrolyte addition (26).…”

Metal-Based Molecular Functional Materials - From Discrete Metal Complexes to Supramolecular Assembly, Nanostructures and Functions

“…[7][8][9][10][11][12][13] In addition, lots of efforts have also been devoted into the exploration of new classes of luminescent transition metalligand chromophores and their application in materials chemistry and science by understanding and rationalization of their excited state properties. [7][8][9][10][11][12][13][14] Therefore the design strategy for molecular functional materials can be extended from the discrete molecules with their intrinsic structural properties to the investigation and 47 The same group has also elaborated the system by functionalization of the terpyridine ligand by attaching an extra phenyl ring such that an intraligand charge transfer (ILCT) excited state can be introduced into the platinum(II) moiety. 48 The incorporation of more electron-donating substituents in the alkynyl resulted in a gradual red shift of the absorption energy, which indicated the substantial involvement of the alkynyl ligand in the lowest energy transition and signifi ed the assignment of admixture of MLCT [dp(Pt) → p*(terpyridine)]…”