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The preparation, physical properties, and photophysical properties of [Pt(bph)(C2H5)zS]zl [Pt(bph)(CH3CN),], [Pt(bph)(en)], and [Pt(bph)(py)z], where bph2-is the dianion of biphenyl, en is ethylenediamine, and py is pyridine, are described. The complexes display d a -A* transitions in the 300-400-nm region and intraligand A -A* transitions at higher energy. Only one redox process, an irreversible oxidation, is observed in the +2 to -2 V region. The Ell2 values range from 0.67 to 1.35 V vs SSCE. Highly structured emission is observed and attributed to a 3LC -+ IGS process. Spectral curve fitting using a four-mode fit gives Em = 20 670 cm-l and vibrational frequencies of 1550, 1150, 715, and 375 cm-1 that are nearly independent of the specific complex. Temperature-dependent lifetime data reveal the presence of an energy level above the 3LC state with an activation energy of 1220 cm-1 for [Pt(bph)(CH3CN)2], 2280 cm-I for [Pt(bph)(py)~], and 2490 cm-I for [Pt(bph)(en)]. The energy gap of -2.6 eV gives rise to high oxidative quenching power (-1.14 to -1.71 V) demonstrated by electron-transfer quenching with methyl viologen and o-nitrobenzene.

The preparation and properties of monometallic and bimetallic complexes of rhenium(I) tricarbonyl chloride coordinated to 4,4'-dimethyl-2,2'-bipyridine ((CH3)2bpy), 2,2'-bipyrimidine (bpm), 2,3-bis(2-pyridyl)pyrazine (bpp), and l,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethane (Mebpy-Mebpy) are described. The CO stretching frequencies were in accord with facial geometry for the complexes. The NMR properties revealed that protons on the carbon atoms a to the coordinating nitrogen atoms of coordinated heterocycles were deshielded and shifted downfield. Electrochemically, one or two irreversible oxidations, a reversible reduction assignable to reduction of the heterocyclic ligand, and a second reduction (irreversible) at a potential more negative than that of the first were observed. The monometallic complexes displayed dir -* ir* transitions in the 360-380-nm region. The transition red-shifted to 454 nm for [(bpp)(Re(CO)3Cl)2] and to 480 nm for [(bpm)(Re(CO)3Cl)2] but remained at 366 nm for [(Mebpy-Mebpy)(Re(CO)3Cl)2], Emission was observed at room temperature for [((CH3)2bpy)Re(CO)3Cl], [(Mebpy-Mebpy)Re(CO)3Cl], [(bpp)Re(CO)3Cl], and [(Mebpy-Mebpy)(Re(CO)3Cl)2], Their emission maxima were located near 600 nm except for [(bpp)Re(CO)3Cl]. Its emission maximum was observed at 700 nm.84ER-13263 and the National Science Foundation under Grant CHE-8719709 for support. Supplementary Material Available: A listing of decoupling parameters, results, and conclusions for NMR experiments with [(Mebpy-Mebpy)-Re(CO)3Cl], [(bpp)Re(CO)3Cl], and [(bpp)(Re(CO)3Cl)2] (4 pages). Ordering information is given on any current masthead page.

The physical and photophysical properties of a series of rhenium(I) tetracarbonyl complexes [Re(CO)4(L-L)]-CF3SO3, where L-L = 2,2'-bipyrimidine (bpm), 4,4'-dimethyl-2,2,-bipyridine (dmb), 2,2'-bipyridine (bpy), and 1,10-phenanthroline (phen), are reported. The complexes displayed reductions but no oxidations within the +2 to -2 V vs SSCE electrochemical window. Electronic absorptions associated with dxx* transitions were observed between 300 and 400 nm; x -*• x* transitions associated with the aromatic heterocyclic ligand were found at wavelengths <300 nm. Excitation at 355 nm resulted in the appearance of emission in solution at room temperature with emission quantum yields near 0.03 for the bpm, bpy, and dmb derivatives and 0.008 for the phen derivative. The bpy, dmb, and phen derivatives displayed structured emission located near 470 nm, while the bpm derivative displayed unstructured emission located near 521 nm. The complexes were photosensitive in methylene chloride, expelling one of the CO ligands. The photochemical quantum yields ranged from 0.03 to 0.9. Reductive quenching was observed with various methoxybenzene compounds and Cl" ion verifying the high [Re(CO)4(L-L)+*/°r edox potentials calculated to be on the order of 1.5 V. An excited-state model assigning structured emission to a 3LC state, unstructured emission to a 3MLCT state, and photosubstitution to a 3LF(dd) state or possibly the 3MLCT state is proposed.