Osmium(II) complexes bearing C,N,C-pincer ligand 2,6-bis(alkylimidazolin-2-ylidene)pyridine (CNC-Me and CNC-Bu for alkyl = methyl and n-butyl, respectively) or 2,6-bis(3-butylbenzimidazolin-2-ylidene)pyridine (CNC 0 -Bu) and aromatic diimine (2,2 0 -bipyridine (bpy)/1,10-phenanthroline (phen)) have been prepared. The X-ray crystal structure of [Os(CNC-Me)(bpy)Cl](PF 6 ) shows that the Os-C bonds are essentially single (Os-C distances = 2.042(4) and 2.059(4) A ˚). Spectroscopic comparisons of [Os(C,N,C)(diimine)Cl] þ and [Os(tpy)(bpy)Cl] þ (tpy = 2,2 0 ;6 0 ,2 00terpyridine) suggest that the lowest-energy absorption bands for [Os(C,N,C)(diimine)Cl] þ originate from a d π (Os II ) f π*(diimine) metal-to-ligand charge-transfer (MLCT) transition. Density functional theory calculations reveal that the π*(diimine) levels in [Os(C,N,C)(diimine)Cl] þ are lower lying than the π*(C,N,C). The Os(II/III) oxidation waves for [Os(C,N,C)(diimine)Cl] þ are reversible, with E 1/2 = -0.03 to 0.16 V vs Cp 2 Fe þ/0 . The absorption spectra for the Os(III) species have been obtained by spectroelectrochemical methods.

T he discovery that nitric oxide plays many fundamental physiological roles has aroused interest in the structures, electronic properties, and reactivities of metal-nitrosyl complexes. [1][2][3][4][5][6][7][8][9][10][11][12][13] The chemistry between NO and organometallic complexes, especially reactions that lead to formation of new carbonnitrogen bonds, is of considerable interest because organic nitroso compounds have been demonstrated to be a class of attractive electrophiles in many carbon-nitrogen and/or carbon-oxygen bond forming reactions. 14-20 In the past few decades, investigations on the insertion of NO into metal-alkyl and metal-aryl bonds to form C-nitroso complexes provided insightful results for the development of metal-mediated organic transformation reactions, 21-36 and the alkyl/aryl moiety migration to the coordinated NO ligand, i.e. R-M-(NO) þ L f L-M-N(dO)R, has been demonstrated to be a critical step in carbon-nitrogen bond formation. Nitrosonium ion (NO þ ), a close relative of NO, is known to react substitutionally with metal complexes to give metal-nitrosyl systems, 8,37-44 although there are several examples proposing that NO þ can insert into metal-carbon bonds in an intermolecular fashion. [25][26][27]31 We herein present a systematic investigation of the reaction between NO þ and 2-phenylpyridine anion (phpy)-ligated cyclometalated ruthenium(II) complexes, which demonstrates for the first time that NO þ inserts into a Ru II -aryl phpy bond to give 2-(2-nitrosophenyl)pyridine (NO-phpy)-coordinated complexes. Experimental evidence supports a direct bimolecular NO þ insertion mechanism, i.e. M-R þ NO þ f [M-N(dO)-R] þ , but not an intramolecular migratory insertion mechanism for the insertion reactions in this work. Moreover, theoretical calculations reveal that direct NO þ insertion into the Ru-C bond may be rationalized as a frontier orbital interaction between the [Ru-aryl]-based HOMO of the Ru(II) complexes and the LUMO of the NO þ . Unlike many literature examples, the non-NO-ligated complexes [Ru(phpy)([9]aneS3)(L)] þ ([9]aneS3 = 1,4,7-trithiacyclononane) were employed to react with NO þ in this study; this can reduce ambiguity in mechanism evaluations. When excess [NO][BF 4 ] (5-fold) was added to [Ru(phpy)([9]aneS3)(solv)] þ (1-solv; solv = CH 3 CN, EtOH) in CH 3 CN under argon at room temperature, the solution changed from yellow to dark red immediately. The dark red product isolated (85% yield) was found to be [Ru(NO-phpy)-([9]aneS3)(CH 3 CN)] 2þ (2-CH 3 CN; NO-phpy = 2-(2-nitrosophenyl)pyridine) by 1 H and 13 C NMR spectroscopy, X-ray crystallography, and elemental analysis (Scheme 1). This reactivity is different from that for other ruthenium(II) complexes which react with NO þ substitutionally to give the ligand-substituted Runitrosyl products. 37,38,40,41,43 Reaction between the S-bound dmso complex [Ru(phpy)([9]aneS3)(dmso)] þ (1-dmso) and [NO]-[BF 4 ] in CH 3 CN also gave 2-CH 3 CN in 80% yield.The X-ray crystal structure for [2-CH 3 CN](PF 6 ) 2 3 CH 3 CN represents the...

Ruthenium(II)-acetylide complexes bearing 1,4,7-trithiacyclononane ([9]aneS3) and 1,10-phenanthroline (phen) have been prepared. The molecular structure of [([9]aneS3)(phen)Ru-CtCPh] þ shows that the trans influence of the acetylide ligand is only slightly weaker than that of isocyanide and is stronger than that of chloride. The Ru(II/III) oxidation waves for the complexes are irreversible, with E pa = 0.30-0.39 V vs Cp 2 Fe þ/0 . The lowest-energy dipole-allowed absorptions for the complexes (λ max = 441-466 nm, ε max = (4-5) Â 10 3 dm 3 mol -1 cm -1 ) are assigned as d π (Ru II ) f π*(phen) metal-to-ligand charge transfer (MLCT) transitions. The complexes are emissive in glassy MeOH/EtOH at 77 K upon photoexcitation and give emission at λ max = 606-623 nm. Density functional theory (DFT) calculations and charge decomposition analysis (CDA) have been used to probe the Ru-C bonding interaction in these complexes, and the results are compared with their isocyanide congeners. The rotational barrier for the phenyl ring in [([9]aneS3)(phen)Ru-CtCPh] þ is calculated to be 0.53 kcal mol -1 , suggesting that the Ru-C π-interaction in these complexes is weak and cannot lock the rotational motion of the acetylide ligand effectively.

Surface plasmons (SPs) and their corresponding optical properties in noble metal nanoparticles have received considerable attention. 1À9 In recent years, there are numerous reports on the application of SPs in the development of molecular sensors, 10À13 organic solar cells, 14 and light-emitting diodes. 15À19 Localized surface plasmons resonance (LSPR), a type of surface plasmon resonances, is an optical resonance phenomenon of nonpropagating excitation of conduction electrons in metallic nanostructures coupled to electromagnetic field. 20 LSPR can affect the optical properties of materials nearby, resulting in either enhancement 15,16,21À23 or quenching 24À26 of the photoluminescence (PL) property of adjacent fluorophore. In noble metallic nanoparticles, LSPR presents strong absorption and scattering cross-section and is sensitive to the local refractive index, size, shape, and chemical compositions of the nanostructures. 27,28 This unique characteristic provides a convenient means to manipulate the PL properties, such as modifying the LSPR bands, by controlling the shape and size of the metal nanoparticles. Recently, researchers have put significant efforts into controlling the shape of noble metal nanoparticles including nanosphere (NS), nanoprism, 29,30 nanocube, 31,32 polyhedron, 33À35 nanorods, and nanowires. 36À39 Silver and gold nanoparticles have been considered as desirable candidates for applications like enhancing the performance of solar cells 40 and biosensing agents 13,41À47 because their LSPR bands are within the visible to near-infrared (NIR) region.Enhancing the emission performance of cadmium chalocogenides (CdX, X = S, Se, or Te) nanoparticles via the assistance of

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