This work describes syntheses and electrochemical, spectroscopic, and bonding properties in a new series of dinuclear ruthenium(II) complexes bridged by polyaromatic (biphenyl, fluorene, phenanthrene, and pyrene) alkynyl ligands. Longitudinal expansion of the π-conjugated polyaromatic core of the bridging ligands caused a reduced potential difference between the anodic steps and reinforced their bridge-localized nature, as evidenced by UV/vis/near-IR and IR spectroelectrochemical data combined with DFT and TDDFT calculations. Importantly, the intricate multiple IR ν(CC) absorption bands for the singly oxidized states imply a thermal population of a range of conformers (rotamers) with distinct electronic character. This behavior was demonstrated with more accurate DFT calculations of selected nontruncated 1e − oxidized complexes in three different conformations. The combined experimental and theoretical data reveal that thermally populated rotamers featuring various mutual orientations of the ligated metal termini and the bridging diethynyl polyaromatic moieties have a significant impact on the electronic absorption and ν(CC) wavenumbers of the singly oxidized systems. ■ INTRODUCTIONSince the first report of the Creutz−Taube ion [(H 3 N) 5 Ru(μ-pyrazine)Ru(NH 3 ) 5 ] 5+ , there have been numerous experimental and theoretical attempts to elaborate the properties of related symmetrical diruthenium complexes due to the surprising stability of the Ru II Ru III mixed-valence states. 1 It has been well documented that diruthenium complexes with metal centers linked by π-conjugated bridges allow for facile electron transfer along the whole molecular framework. Accordingly, pertinent studies have concentrated on elaborately selecting the conjugated bridging ligands and tuning the electronic effect of the ancillary ligands to subtly modulate the intramolecular electron-transfer properties in mixed-valence complexes. 2,3 We have focused on dinuclear ruthenium complexes with a particular type of redox-active terminals, viz., (P,P′-dppe)(η 5 -C 5 Me 5 )Ru, which are interconnected by the conjugated bridge participating in the redox behavior. These complexes may become attractive candidates for molecular wires. 4 Furthermore, a range of studies in our laboratory as well as other literature reports have convincingly elucidated that the horizontal scaling of π-conjugated bridges results in poor solubility and chemical stability of the oxidized species and an attenuation of the electronic transport in a mixed-valence system; introducing aromatic rings such as benzene or a heterocycle in the spacer can constitute an attractive alternative to improve this instability and eventually to tune their physical or even chemical properties. 5 Therefore, a reasonable control of the length and appropriate extension of the conjugation in the bridging ligands can afford improved stability and allow for efficient tuning of the electron-transfer properties. 6 In addition, numerous studies have indicated that fluorene, phenanthrene, and pyrene ...

A series of dinuclear ruthenium alkynyl and vinyl complexes bridged by carbazole, dibenzofuran, dibenzothiophene, and fluorenone have been prepared, and some representative molecular structures have been determined. The electrochemical and spectroscopic properties of the compounds were explored by cyclic voltammetry (CV), square-wave voltammetry (SWV), and in situ infrared and UV/Vis/near-IR spectroelectrochemical methods. The electrochemical results

A series of ruthenium(ii) complexes [{RuCl(CO)(PMe3)3(-CH[double bond, length as m-dash]CH-)}nX], (: n = 3, X = 3,3''-dimethyl-2,2':3',2''-terthiophene; : n = 2, X = 2,2'-bithiophene; : n = 2, X = 2,3-bis(3-methylthiophen-2-yl)benzothiophene) and [{Cp*(dppe)2Ru(-C[triple bond, length as m-dash]C-)}3X], (X = 3,3''-dimethyl-2,2':3',2''-terthiophene), were prepared and characterized by (1)H, (13)C and (31)P NMR. Their redox, spectroscopic and bonding properties were studied with a range of spectro-electrochemical methods in combination with density functional theory calculations. The first two anodic steps observed for and are largely localized on the lateral frameworks of the molecular triangle, the direct conjugation between them being precluded due to the photostable open form of the dithienyl ethene moiety. The third anodic step is then mainly localized on the centerpiece of the triangular structure, affecting both bithiophene laterals. The experimental IR and UV-vis-NIR spectroelectrochemical data and, largely, also DFT calculations account for this explanation, being further supported by direct comparison with the anodic behavior of reference diruthenium complexes and .

To determine the allelopathic effects of root exudates from Flaveria bidentis on function of Bacillus, pot experiment was used to collect root exudates from living plants and test its allelopathic effects on function of Bacillus frigoritolerans and Bacillus megaterium, which were two dominant bacteria in the rhizosphere soil of F. bidentis. To obtain the allelopathic substances, the root exudates were successively extracted by N-hexane, dichloromethane, ethyl acetate, and N-butanol, and their allelopathic effects were tested. The results showed that B. frigoritolerans and B. megaterium considerably increased the concentration of available phosphorus and nitrogen, respectively, when the soil was treated with different concentrations of root exudates. Among the four organic solvent extracts, dichloromethane extracts significantly increased the abundances of B. frigoritolerans and B. megaterium and promoted their nitrogen-fixing and phosphate-solubilizing abilities. Phenol was detected in dichloromethane extracts by gas chromatograph-mass spectrometer (GC-MS). Meanwhile, phenol promoted the ability to fix nitrogen of B. megaterium and its growth by increasing the soil available nitrogen concentration, but phenol promoted the ability to solubilize phosphate of B. frigoritolerans only in 0.1mg/mL concentration. Therefore, phenol was an allelochemicals in the root exudates of F. bidentis that affects the growth and activities of B. megaterium.