Formation and structural chemistry of the unusual cyanide-bridged dinuclear species [Ru-2(NN)(2)(CN)(7)](3-)(NN=2,2 '-bipyridine or 1,10-phenanthroline)

Crystallisation of simple cyanoruthenate complex anions [Ru(NN)(CN)(4)](2) (NN = 2,2'-bipyridine or 1,10-phenanthroline) in the presence of Lewis-acidic cations such as Ln(III) or guanidinium cations results, in addition to the expected [Ru(NN)(CN)(4)](2) salts, in the formation of small amounts of salts of the dinuclear species [Ru-2(NN)(2)(CN)(7)](3). These cyanide-bridged anions have arisen from the combination of two monomer units [Ru(NN)(CN)(4)](2) following the loss of one cyanide, presumably as HCN. The crystal structures of [Nd(H2O)(5.5)][Ru-2(bipy)(2)(CN)(7)] center dot 11H(2)O and [Pr(H2O)(6)][Ru-2(phen)(2)(CN)(7)] center dot 9H(2)O show that the cyanoruthenate anions form Ru-CN-Ln bridges to the Ln(III) cations, resulting in infinite coordination polymers consisting of fused Ru(2)Ln(2)(mu-CN)(4) squares and Ru(4)Ln(2)(mu-CN)(6) hexagons, which alternate to form a one-dimensional chain. In [CH6N3](3)[Ru-2(bipy)(2)(CN)(7)] center dot 2H(2)O in contrast the discrete complex anions are involved in an extensive network of hydrogen-bonding involving terminal cyanide ligands, water molecules, and guanidinium cations. In the [Ru-2(NN)(2)(CN)(7)](3) anions themselves the two NN ligands are approximately eclipsed, lying on the same side of the central Ru-CN-Ru axis, such that their peripheries are in close contact. Consequently, when NN = 4,4'-Bu-t(2)-2,2'-bipyridine the steric bulk of the t-butyl groups prevents the formation of the dinuclear anions, and the only product is the simple salt of the monomer, [CH6N3](2)[Ru((t)Bu(2)bipy)(CN)(4)] center dot 2H(2)O. We demonstrated by electrospray mass spectrometry that the dinuclear by-product [Ru-2(phen)(2)(CN)(7)](3) could be formed in significant amounts during the synthesis of monomeric [Ru(phen)(CN)(4)](2) if the reaction time was too long or the medium too acidic. In the solid state the luminescence properties of [Ru-2(bipy)(2)(CN)(7)](3) (as its guanidinium salt) are comparable to those of monomeric [Ru(bipy)(CN)(4)](2), with a (MLCT)-M-3 emission at 581 nm

An improved synthesis, crystal structures, and metallochromism of salts of [Ru(tolyl-terpy)(CN)(3)](-)

The previously reported complex [Ru(ttpy)(CN)(3)] [ttpy = 4'(p-tolyl)-2,2':6',2"-terpyridine] is conveniently synthesised by reaction of ttpy with Ru(dmso)(4)Cl-2 to give [Ru(ttpy)(dmso)Cl-2], which reacts in turn with KCN in aqueous ethanol to afford [Ru(ttpy)(CN)(3)] which was isolated and crystallographically characterised as both its (PPN)(+) and K+ salts. The K+ salt contains clusters containing three complex anions and three K+ cations connected by end-on and side-on cyanide ligation to the K+ ions. The solution speciation behaviour of [Ru(ttpy)(CN)(3)] was investigated with both Zn2+ and K+ salts in MeCN, a solvent sufficiently non-competitive to allow the added metal cations to associate with the complex anion via the externally-directed cyanide lone pairs. UV-Vis spectroscopic titration of (PPN)[Ru(ttpy)(CN)(3)] with Zn(ClO4)(2) showed a blue shift of 2900 cm (1) in the (MLCT)-M-1 absorption manifold due to the ` metallochromism' effect; a series of distinct binding events could be discerned corresponding to formation of 4:1, 1:1 and then 1:3 anion: cation adducts, all with high formation constants, as the titration proceeded. In contrast titration of (PPN)[Ru(ttpy)(CN)(3)] with the more weakly Lewis-acidic KPF6 resulted in a much smaller blue-shift of the 1MLCT absorptions, and the titration data corresponded to formation of 1:1 and then 2: 1 cation: anion adducts with weaker stepwise association constants of the order of 10(4) and then 10(3) M (1). Although association of [Ru(ttpy)(CN)(3)] resulted in a blue-shift of the (MLCT)-M-1 absorptions, the luminescence was steadily quenched, as raising the (MLCT)-M-3 level makes radiationless decay via a lowlying (MC)-M-3 state possible. (C) 2010 Elsevier B. V. All rights reserved

Bridged graphite oxide materials

Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media

The Jurassic rise of squamates as supported by lepidosaur disparity and evolutionary rates

The squamates (lizards, snakes, and relatives) today comprise more than 10,000 species, and yet their sister group, the Rhynchocephalia, is represented by a single species today, the tuatara. The explosion in squamate diversity has been tracked back to the Cretaceous Terrestrial Revolution, 100 million years ago (Ma), the time when flowering plants began their takeover of terrestrial ecosystems, associated with diversification of coevolving insects and insect-eating predators such as lizards, birds, and mammals. Squamates arose much earlier, but their long pre-Cretaceous history of some 150 million years (Myr) is documented by sparse fossils. Here, we provide evidence for an initial radiation of squamate morphology in the Middle and Late Jurassic (174-145 Ma), and show that they established their key ecological roles much earlier than had been assumed, and they have not changed them much since

Coupled Natural Fusion Enzymes in a Novel Biocatalytic Cascade Convert Fatty Acids to Amines

[Image: see text] Tambjamine YP1 is a pyrrole-containing natural product. Analysis of the enzymes encoded in the Pseudoalteromonas tunicata “tam” biosynthetic gene cluster (BGC) identified a unique di-domain biocatalyst (PtTamH). Sequence and bioinformatic analysis predicts that PtTamH comprises an N-terminal, pyridoxal 5′-phosphate (PLP)-dependent transaminase (TA) domain fused to a NADH-dependent C-terminal thioester reductase (TR) domain. Spectroscopic and chemical analysis revealed that the TA domain binds PLP, utilizes l-Glu as an amine donor, accepts a range of fatty aldehydes (C(7)–C(14) with a preference for C(12)), and produces the corresponding amines. The previously characterized PtTamA from the “tam” BGC is an ATP-dependent, di-domain enzyme comprising a class I adenylation domain fused to an acyl carrier protein (ACP). Since recombinant PtTamA catalyzes the activation and thioesterification of C(12) acid to the holo-ACP domain, we hypothesized that C(12) ACP is the natural substrate for PtTamH. PtTamA and PtTamH were successfully coupled together in a biocatalytic cascade that converts fatty acids (FAs) to amines in one pot. Moreover, a structural model of PtTamH provides insights into how the TA and TR domains are organized. This work not only characterizes the formation of the tambjamine YP1 tail but also suggests that PtTamA and PtTamH could be useful biocatalysts for FA to amine functional group conversion

On the bioeconomics of marine reserves when dispersal evolves

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Natural Resource Modeling 28 (2015): 456-474, doi:10.1111/nrm.12075.Marine reserves are an increasingly used and potentially contentious tool in fisheries management. Depending upon the way that individuals move, no-take marine reserves can be necessary for maximizing equilibrium rent in some simple mathematical models. The implementation of no-take marine reserves often generates a redistribution of fishing effort in space. This redistribution of effort, in turn, produces sharp spatial gradients in mortality rates for the targeted stock. Using a two-patch model, we show that the existence of such gradients is a sufficient condition for the evolution of an evolutionarily stable conditional dispersal strategy. Thus, the dispersal strategy of the fish depends upon the harvesting strategy of the manager and vice versa. We find that an evolutionarily stable optimal harvesting strategy (ESOHS)—one which maximizes equilibrium rent given that fish disperse in an evolutionarily stable manner– - never includes a no-take marine reserve. This strategy is economically unstable in the short run because a manager can generate more rent by disregarding the possibility of dispersal evolution. Simulations of a stochastic evolutionary process suggest that such a short-run, myopic strategy performs poorly compared to the ESOHS over the long run, however, as it generates rent that is lower on average and higher in variability.This material is based upon work supported by funding from: The Woods Hole Oceanographic Institution's Investment in Science Fund to MGN; The Recruitment Program of Global Experts to YL; The University of Tennessee Center for Business and Economics Research to SL; and the U.S. National Science Foundation (NSF) through grants OCE-1031256, DEB-1257545, and DEB-1145017 to MGN, CNH-0707961 to GEH, DMS-1411476 to YL; and NSF Graduate Research Fellowships under Grant No. 1122374 to EAM and ES

Defying the Tone at the Top: An Analysis on the Effects of Board Characteristics on the Level of Tax Avoidance Across Philippine Publicly Listed Firms

Over the years, the growing culture of tax avoidance among multinational companies around the world has shed light on the importance of improving corporate governance mechanisms. In the Philippines, poor tax collection due to tax leakages has contributed to chronic fiscal deficits in the country. The literature argues that good corporate governance mechanisms (e.g., the structure of the board of directors) play a significant role in ensuring that the management acts in the best interest of the firm and shareholders, thus eventually helping to mitigate the incidences of corporate tax avoidance. Specifically, agency theory argues that the presence of more independent- and female-dominated boards lead to lesser corporate tax avoidance because such directors are stricter in monitoring management. On the other hand, the resource dependency theory posits that firms with boards having more independent, older, and business-educated directors are more likely to engage in tax avoidance because such directors have the experience, expertise, and knowhow to engage in tax avoidance strategies. This paper examines the impact of various board characteristics on the incidence of tax avoidance across nonfinancial and publicly-traded Philippine firms during the period 2003 to 2015. We use the residual book-tax gap, the cash-effective tax rate, and the long run effective tax rate to measure corporate tax avoidance, whereas board characteristics include board size, board age, board independence, CEO-Chair duality, gender diversity, and the educational background of directors. We employ the two-step Blundell-Bond System Generalized Method of Moments (GMM) estimation technique to address endogeneity issues that may confound the relationship between board composition and structure and the level of tax avoidance within the firm. Overall, we find no significant relationship between board characteristics and tax avoidance, as measured by the long-run cash effective tax rates. However, consistent with the agency and resource dependency theories, we find that board age is positively related with corporate tax avoidance, as measured by the residual book-tax gap, whereas board independence and the proportion of board members with post-graduate degrees in Business and Economics have a negative and positive relationship, respectively, when corporate tax avoidance is proxied by the cash effective tax rate. These findings suggest that the case for increasing the number of independent directors and reducing the number of older directors in boards of Philippine publicly listed firms may help reduce incidences of corporate tax avoidance