Collybistin SH3-protein isoforms are expressed in the rat brain promoting gephyrin and GABA-A receptor clustering at GABAergic synapses.

Collybistin (CB) is a guanine nucleotide exchange factor (GEF) selectively localized at GABAergic and glycinergic postsynapses. Analysis of mRNA shows that several isoforms of collybistin are expressed in the brain. Some of the isoforms have a SH3 domain (CBSH3+) and some have no SH3 domain (CBSH3-). The CBSH3+ mRNAs are predominantly expressed over CBSH3-. However, in an immunoblot study of mouse brain homogenates, only CBSH3+ protein isoforms were detected, proposing that CBSH3- protein might not be expressed in the brain. The expression or lack of expression of CBSH3- protein is an important issue because CBSH3- has a strong effect in promoting the postsynaptic clustering of gephyrin and GABA-A receptors (GABAA Rs). Moreover CBSH3- is constitutively active; therefore lower expression of CBSH3- protein might play a relatively stronger functional role than the more abundant but self-inhibited CBSH3+ isoforms, which need to be activated. We are now showing that: (a) CBSH3- protein is expressed in the brain; (b) parvalbumin positive (PV+) interneurons show higher expression of CBSH3- protein than other neurons; (c) CBSH3- is associated with GABAergic synapses in various regions of the brain and (d) knocking down CBSH3- in hippocampal neurons decreases the synaptic clustering of gephyrin and GABAA Rs. The results show that CBSH3- protein is expressed in the brain and that it plays a significant role in the size regulation of the GABAergic postsynapse.

In vivo cytochrome P450 activity alterations in diabetic nonalcoholic steatohepatitis mice.

Nonalcoholic steatohepatitis (NASH) has been identified as a source of significant interindividual variation in drug metabolism. A previous ex vivo study demonstrated significant changes in hepatic Cytochrome P450 (CYP) activity in human NASH. This study evaluated the in vivo activities of multiple CYP isoforms simultaneously in prominent diabetic NASH mouse models. The pharmacokinetics of CYP selective substrates: caffeine, losartan, and omeprazole changed significantly in a diabetic NASH mouse model, indicating attenuation of the activity of Cyp1a2 and Cyp2c29, respectively. Decreased mRNA expression of Cyp1a2 and Cyp2c29, as well as an overall decrease in CYP protein expression, was found in the diabetic NASH mice. Overall, these data suggest that the diabetic NASH model only partially recapitulates the human ex vivo CYP alteration pattern. Therefore, in vivo determination of the effects of NASH on CYP activity should be conducted in human, and more appropriate models are required for future drug metabolism studies in NASH.

Effect of axial ligands on the spectroscopic and electrochemical properties of diruthenium compounds.

Three related diruthenium complexes containing four symmetrical anionic bridging ligands were synthesized and characterized as to their electrochemical and spectroscopic properties. The examined compounds are represented as Ru2(dpb)4Cl, Ru2(dpb)4(CO), and Ru2(dpb)4(NO) in the solid state, where dpb = diphenylbenzamidinate anion. Different forms of Ru2(dpb)4Cl are observed in solution depending on the utilized solvent and the counteranion added to solution. Each Ru2(5+) form of the compound undergoes multiple redox processes involving the dimetal unit. The reversibility as well as potentials of these diruthenium-centered electrode reactions depends upon the solvent and the bound axial ligand. The Ru2(5+/4+) and Ru2(5+/6+) processes of Ru2(dpb)4Cl were monitored by UV-vis spectroscopy in both CH2Cl2 and PhCN. A conversion of Ru2(dpb)4Cl to [Ru2(dpb)4(CO)](+) was also carried out by simply bubbling CO gas through a CH2Cl2 solution of Ru2(dpb)4Cl at room temperature. The chemically generated [Ru2(dpb)4(CO)](+) complex undergoes several electron transfer processes in CH2Cl2 containing 0.1 M TBAClO4 under a CO atmosphere, and the same reactions were seen for a chemically synthesized sample of Ru2(dpf)4(CO) in CH2Cl2, 0.1 M TBAClO4 under a N2 atmosphere, where dpf = N,N'-diphenylformamidinate anion. Ru2(dpb)4(NO) undergoes two successive one-electron reductions and a single one-electron oxidation, all of which involve the diruthenium unit. The CO and NO adducts of Ru2(dpb)4 were further characterized by FTIR spectroelectrochemistry, and the IR spectral data of these compounds are discussed in light of results for previously characterized Ru2(dpf)4(CO) and Ru2(dpf)4(NO) derivatives under similar solution conditions.

Zebrafish Retinal Ganglion Cells Asymmetrically Encode Spectral and Temporal Information across Visual Space.

In vertebrate vision, the tetrachromatic larval zebrafish permits non-invasive monitoring and manipulating of neural activity across the nervous system in vivo during ongoing behavior. However, despite a perhaps unparalleled understanding of links between zebrafish brain circuits and visual behaviors, comparatively little is known about what their eyes send to the brain via retinal ganglion cells (RGCs). Major gaps in knowledge include any information on spectral coding and information on potentially critical variations in RGC properties across the retinal surface corresponding with asymmetries in the statistics of natural visual space and behavioral demands. Here, we use in vivo two-photon imaging during hyperspectral visual stimulation as well as photolabeling of RGCs to provide a functional and anatomical census of RGCs in larval zebrafish. We find that RGCs' functional and structural properties differ across the eye and include a notable population of UV-responsive On-sustained RGCs that are only found in the acute zone, likely to support visual prey capture of UV-bright zooplankton. Next, approximately half of RGCs display diverse forms of color opponency, including many that are driven by a pervasive and slow blue-Off system-far in excess of what would be required to satisfy traditional models of color vision. In addition, most information on spectral contrast was intermixed with temporal information. Taken together, our results suggest that zebrafish RGCs send a diverse and highly regionalized time-color code to the brain.

Expression of protocadherin-γC4 protein in the rat brain.

It has been proposed that the combinatorial expression of γ-protocadherins (Pcdh-γs) and other clustered protocadherins (Pcdhs) provides a code of molecular identity and individuality to neurons, which plays a major role in the establishment of specific synaptic connectivity and formation of neuronal circuits. Particular attention has been directed to the Pcdh-γ family, for which experimental evidence derived from Pcdh-γ-deficient mice shows that they are involved in dendrite self-avoidance, synapse development, dendritic arborization, spine maturation, and prevention of apoptosis of some neurons. Moreover, a triple-mutant mouse deficient in the three C-type members of the Pcdh-γ family (Pcdh-γC3, Pcdh-γC4, and Pcdh-γC5) shows a phenotype similar to the mouse deficient in whole Pcdh-γ family, indicating that the latter is largely due to the absence of C-type Pcdh-γs. The role of each individual C-type Pcdh-γ is not known. We have developed a specific antibody to Pcdh-γC4 to reveal the expression of this protein in the rat brain. The results show that although Pcdh-γC4 is expressed at higher levels in the embryo and earlier postnatal weeks, it is also expressed in the adult rat brain. Pcdh-γC4 is expressed in both neurons and astrocytes. In the adult brain, the regional distribution of Pcdh-γC4 immunoreactivity is similar to that of Pcdh-γC4 mRNA, being highest in the olfactory bulb, dentate gyrus, and cerebellum. Pcdh-γC4 forms puncta that are frequently apposed to glutamatergic and GABAergic synapses. They are also frequently associated with neuron-astrocyte contacts. The results provide new insights into the cell recognition function of Pcdh-γC4 in neurons and astrocytes.

Electrochemical and spectroscopic characterization of a series of mixed-ligand diruthenium compounds.

The electrochemistry and spectroelectrochemistry of a novel series of mixed-ligand diruthenium compounds were examined. The investigated compounds having the formula Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl where x = 1-3 and Fap is 2-(2-fluoroanilino)pyridinate anion were made from the reaction of Ru(2)(CH(3)CO(2))(4)Cl with 2-(2-fluoroanilino)pyridine (HFap) in refluxing methanol. The previously characterized Ru(2)(Fap)(4)Cl as well as the three newly isolated compounds represented as Ru(2)(CH(3)CO(2))(Fap)(3)Cl (1), Ru(2)(CH(3)CO(2))(2)(Fap)(2)Cl (2), and Ru(2)(CH(3)CO(2))(3)(Fap)Cl (3) possess three unpaired electrons with a Ru(2)(5+) dimetal core. Complexes 1 and 2 have well-defined Ru(2)(5+/4+) and Ru(2)(5+/6+) redox couples in CH(2)Cl(2), but 3 exhibits a more complicated electrochemical behavior due to equilibria involving association or dissociation of the anionic chloride axial ligand on the initial and oxidized or reduced forms of the compound. The E(1/2) values for the Ru(2)(5+/4+) and Ru(2)(5+/6+) processes vary linearly with the number of CH(3)CO(2)(-) bridging ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl and plots of reversible half-wave potentials vs the number of acetate groups follow linear free energy relationships with the largest substituent effect being observed for the oxidation. The major UV-visible band of the examined compounds in their neutral Ru(2)(5+) form is located between 550 and 800 nm in CH(2)Cl(2) and also varies linearly with the number of CH(3)CO(2)(-) ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl. The electronic spectra of the singly oxidized and singly reduced forms of each diruthenium species were characterized by UV-visible spectroelectrochemistry in CH(2)Cl(2).

Interconversion between (3,1) and (4,0) Isomers of Ru2(L)4X complexes where L is 2-anilinopyridinate or 2-(2,4,6-trifluoroanilino)pyridinate anion and X = Cl- or C[triple bond]CC5H4N-.

A reaction between the (4,0) isomer of Ru 2(ap) 4Cl and LiC[triple bond]CC5H4N leads to a (3,1) isomer of Ru 2(ap) 4(C[triple bond]CC5H4N) 2 1 (ap = anilinopyridinate anion), whereas a reaction involving the (3,1) isomer of Ru 2(F 3ap) 4Cl and TBACl.H 2O leads to (4,0) Ru 2(F 3ap) 4Cl 2 (F 3ap = 2-(2,4,6-trifluoroanilino)pyridinate anion). To our knowledge, these are the first documented examples for isomeric conversion involving diruthenium compounds with tetracarboxylate-type structures. The structural, electrochemical, and spectroscopic properties of 1 and 2 were examined. The reversible Ru 2 (5+/6+) process of (3,1) [Ru 2(F 3ap) 4Cl] (+) is located at 0.62 V in CH 2Cl 2, 0.1 M TBAP but shifts to 0.29 V upon formation of (3,1) Ru 2(F 3ap) 4Cl 2 in CH 2Cl 2 containing chloride from added TBACl.H 2O and shifts even further to E 1/2 = 0.10 V after generation of (4,0) Ru 2(F 3ap) 4Cl 2 in solution. The 190 mV potential difference between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl 2 and (4,0) Ru 2(F 3ap) 4Cl 2 in chloride-containing media can be compared to a smaller potential difference of only 60 mV between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl and (4,0) Ru 2(F 3ap) 4Cl in CH 2Cl 2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) as supporting electrolyte. The larger Delta E 1/2 in the case of the bis-chloride complexes in solutions containing 0.1 M TBACl.H 2O can be accounted for in large part by structural differences that manifest themselves in different strengths of axial coordination to the Ru 2 (5+) form of the compounds.

In vivo transgenic expression of collybistin in neurons of the rat cerebral cortex.

Collybistin (CB) is a guanine nucleotide exchange factor selectively localized to γ-aminobutyric acid (GABA)ergic and glycinergic postsynapses. Active CB interacts with gephyrin, inducing the submembranous clustering and the postsynaptic accumulation of gephyrin, which is a scaffold protein that recruits GABAA receptors (GABAA Rs) at the postsynapse. CB is expressed with or without a src homology 3 (SH3) domain. We have previously reported the effects on GABAergic synapses of the acute overexpression of CBSH3- or CBSH3+ in cultured hippocampal (HP) neurons. In the present communication, we are studying the effects on GABAergic synapses after chronic in vivo transgenic expression of CB2SH3- or CB2SH3+ in neurons of the adult rat cerebral cortex. The embryonic precursors of these cortical neurons were in utero electroporated with CBSH3- or CBSH3+ DNAs, migrated to the appropriate cortical layer, and became integrated in cortical circuits. The results show that: 1) the strength of inhibitory synapses in vivo can be enhanced by increasing the expression of CB in neurons; and 2) there are significant differences in the results between in vivo and in culture studies. J. Comp. Neurol. 525:1291-1311, 2017. © 2016 Wiley Periodicals, Inc.

Synthesis, structure, and electrochemical characterization of a mixed-ligand diruthenium(III,II) complex with an unusual arrangement of the bridging ligands.

A mixed-ligand metal-metal bonded diruthenium complex having the formula Ru(2)(2,4,6-(CH(3))(3)ap)(3)(O(2)CCH(3))Cl where ap is the anilinopyridinate anion was synthesized from the reaction of Ru(2)(O(2)CCH(3))(4)Cl and H(2,4,6-(CH(3))(3)ap), after which the isolated product was structurally, spectroscopically and electrochemically characterized. The crystal structure reveals an unusual arrangement of the bridging ligands around the dimetal unit where one ruthenium atom is coordinated to one anilino and two pyridyl nitrogen atoms while the other ruthenium atom is coordinated to one pyridyl and two anilino nitrogen atoms. To our knowledge, Ru(2)(2,4,6-(CH(3))(3)ap)(3)(O(2)CCH(3))Cl is the only example of a mixed-ligand diruthenium complex of the type [Ru(2)L(3)(O(2)CCH(3))](+), where L is an unsymmetrical anionic bridging ligand that has been structurally characterized with a "(2,1)" geometric conformation of the bridging ligands, all others being "(3,0)". The initial Ru(2)(5+) compound in CH(2)Cl(2) or CH(3)CN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) undergoes up to four one-electron redox processes involving the dimetal unit. The Ru(2)(5+/4+) and Ru(2)(5+/6+) processes were characterized under N(2) using thin-layer UV-visible spectroelectrochemistry and this data is compared to UV-visible spectral changes obtained during similar electrode reactions for related diruthenium compounds having the formula Ru(2)L(4)Cl or Ru(2)L(3)(O(2)CCH(3))Cl where L is an anionic bridging ligand. Ru(2)(2,4,6-(CH(3))(3)ap)(3)(O(2)CCH(3))Cl was also examined by UV-visible and FTIR spectroelectrochemistry under a CO atmosphere and two singly reduced Ru(2)(4+) species, [Ru(2)(2,4,6-(CH(3))(3)ap)(3)(O(2)CCH(3))(CO)Cl](-) and Ru(2)(2,4,6-(CH(3))(3)ap)(3)(O(2)CCH(3))(CO) were in situ generated for further characterization. The CO-bound complexes could be further reduced and exhibited additional reductions to their Ru(2)(3+) and Ru(2)(2+) oxidation states.

Factors predicting the need for splenectomy in children with blunt splenic trauma.

BACKGROUND/PURPOSE: Non-operative management of blunt splenic trauma (BST) in children is the standard of care with a success rate of greater than 90%. This paper aims to determine the factors which could predict the need for operative intervention in children with BST. METHODS: Prospectively entered data of 69 children with BST, between 1997 and 2008, from a single tertiary level trauma centre, were retrospectively analysed. A radiologist blinded to the outcome reviewed all computed tomography scans retrospectively. RESULTS: Forty-two children had isolated BST (61%) and 27 children had associated injuries (39%). All except one survived the injury and non-operative treatment was successful in 91%. Six of the 69 children (9%) with BST underwent splenectomy. There was no independent correlation to age, gender, mechanism of injury (MOI), injury grade and the need for splenectomy, whereas haemodynamic instability within 6 h of injury defined as failed resuscitation had a 100% correlation. CONCLUSION: Haemodynamic instability, which failed to respond to resuscitation within 6 h, predicted the need for splenectomy in children with BST. Splenic injury grade assessed by computed tomography scan does not predict the need for splenectomy.

Synthesis and characterization of (3,1) Ru2(F3ap)4(NCS) and (3,1) Ru2(F3ap)3(F2Oap)(NCS) where F3ap is the 2-(2,4,6-trifluoroanilino)pyridinate anion.

Two isothiocyanate diruthenium complexes, (3,1) Ru2(F3ap)4(NCS) 1 and (3,1) Ru2(F3ap)3(F2Oap)(NCS)2 (where F3ap=2,4,6-trifluoroanilinopyridinate anion), were synthesized from (3,1) Ru2(F3ap)4Cl and SCN(-) under different experimental conditions. Each compound was examined as to its structural, electrochemical, spectroscopic, and magnetic properties. Compound 1 contains three unpaired electrons as its parent compound but 2 is diamagnetic. The X-ray molecular structures of 1 and 2 reveal that the NCS group is coordinated to the dimetal unit via nitrogen in both compounds with the Ru-N-C bond angle being 176.5 degrees for 1 and 166.0 degrees for 2. An elongation of the Ru-Ru bond distance and a shortening of both the Ru-Np (p=pyridyl) and the Ru-Na (a=anilino) bond lengths is seen upon going from (3,1) Ru2(F3ap)4Cl to 2, but the conversion of (3,1) Ru2(F3ap)4Cl to 1 does not affect significantly structural features of the Ru2(L) 4 framework. Compound 1 undergoes one reduction and two oxidations, all three of which involve the dimetal core, whereas 2 undergoes two metal-centered reductions, one metal-centered oxidation, and one ligand-based oxidation due to the presence of the F2Oap ligand on the Ru2 complex. The reactivity of 1 with SCN(-) was also investigated.

Paternal uniparental isodisomy for chromosome 14 with mosaicism for a supernumerary marker chromosome 14.

Uniparental disomy (UPD) describes the inheritance of two homologous chromosomes from a single parent. Disease phenotypes associated with UPD and chromosomal imprinting, rather than with mutations, include Beckwith-Wiedemann syndrome (paternal UPD11p), Angelman syndrome (paternal UPD15), Prader-Willi syndrome (maternal UPD15), and transient neonatal diabetes (paternal UPD6). Here we report on the first case of paternal uniparental isodisomy of chromosome 14 with a mosaicism for a supernumerary marker chromosome 14. The patient demonstrated a small thorax with a 'coat hanger' shape of the ribs, kyphoscoliosis, hypoplasia of the maxilla and mandible, a broad nasal bridge with anteverted nares, contractures of the wrists with ulnar deviation bilaterally, diastasis recti, and marked muscle hypotonia. Vertical skin creases under the chin and stippled epiphyses of the humeri were features not previously described in patients with paternal UPD14. This case illustrates that as with the finding of an isochromosome, a supernumerary marker chromosome can be an important clue to the presence of UPD14.

Synthesis, characterization, and electrochemistry of diruthenium(III,II) and monoruthenium(III) complexes containing pyridyl-substituted 2-anilinopyridinate ligands.

Reaction of the metal-metal bonded complex Ru(2)(O2CCH3)4Cl with 2-anilino-4-methylpyridine leads to the (3,1) isomer of the diruthenium(III,II) complex Ru2(ap-4-Me)4Cl, 1 while the same reaction with 2-anilino-6-methylpyridine gives the monoruthenium(III) derivative Ru(ap-6-Me)3, 2. Both compounds were examined as to their structural, electrochemical, and UV-visible properties, and the data were then compared to that previously reported for (4,0) Ru2(2-Meap)4Cl and other (3,1) isomers of Ru2(L)4Cl with similar anionic bridging ligands. ESR spectroscopy indicates that the monoruthenium derivative 2 contains low-spin Ru(III), and the presence of a single ruthenium atom is confirmed by an X-ray structure of the compound. The combined electrochemical and UV-vis spectroelectrochemical data indicate that the diruthenium complex 1 is easily converted to its Ru2(4+) and Ru2(6+) forms upon reduction or oxidation by one electron while the monoruthenium derivative 2 also undergoes metal-centered redox processes to give Ru(II) and Ru(IV) complexes under the same solution conditions. The reactivity of 1 with CO and CN- was also examined.

"What's my DNA worth, anyway?": a response to the commercialization of individuals' DNA information.

Extensive enthusiasm surrounds the potential for human DNA information to sustain and enhance the pharmaceutical industry's profitability. Nevertheless, persons whose health makes their DNA of commercial interest are routinely expected simply to give their DNA and the information in it to pharmaceutical or genomics companies or their academic intermediaries, voluntarily and without compensation. This state of affairs is increasingly recognized as paradoxical, but it is favored by conventional bioethical opinion. Given that most DNA information is now collected for commercial purposes and is worth considerably more than is generally imagined, bioethical objections to compensation of individuals for their DNA information are inappropriate. This paper suggests approaches by which individuals and representative governments and patient interest groups can negotiate compensation. Appreciable attitudinal change is required if those individuals personally involved are to be included fairly in the commercialization of human DNA information. Ultimately, however, such change is necessary if commercial genetic research is to respect human dignity and human rights.

Factors affecting the electrochemical and spectroelectrochemical properties of diruthenium(III,II) complexes containing four identical unsymmetrical bridging ligands.

Factors affecting the electrochemical and spectroelectrochemical properties of diruthenium(III,II) complexes containing four unsymmetrical bridging ligands are reported for seven related compounds which were isolated in one or two of the four possible isomeric forms. The investigated compounds are represented as Ru(2)(2-CH(3)ap)(4)Cl, Ru(2)(2,5-F(2)ap)(4)Cl, Ru(2)(2,6-F(2)ap)(4)Cl, and Ru(2)(2,4,6-F(3)ap)(4)Cl where 2-CH(3)ap, 2,5-F(2)ap, 2,6-F(2)ap, and 2,4,6-F(3)ap are, respectively, the 2-(2-methylanilino)pyridinate anion, the 2-(2,5-difluoroanilino)pyridinate anion, the 2-(2,6-difluoroanilino)pyridinate anion, and the 2-(2,4,6-trifluoroanilino)pyridinate anion. Ru(2)(2-CH(3)ap)(4)Cl and Ru(2)(2,5-F(2)ap)(4)Cl exist only in a (4,0) conformation while Ru(2)(2,4,6-F(3)ap)(4)Cl is present in both (3,1) and (4,0) isomeric forms. Ru(2)(2,6-F(2)ap)(4)Cl also exists in two isomeric forms, but only the (3,1) isomer was generated in sufficient quantities to be isolated and structurally characterized. This series of seven closely related metal-metal bonded complexes thus provides the first possibility to systematically examine how differences in position and number of the electron-donating or electron-withdrawing groups on the anionic bridging ligands might be related to the electronic properties and structural features of the compound as well as the type and number of geometric isomers which are formed. Each diruthenium derivative undergoes three one-electron transfers in CH(2)Cl(2) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The first reduction and first oxidation products were characterized by thin-layer UV-vis spectroelectrochemistry, and the spectroscopic data, along with E(1/2) values, were then related via linear free energy relationships to the type of isomer and/or position of the electron-donating or electron-withdrawing substituents on the anionic ap bridge. The electrogenerated Ru(2)(6+) and Ru(2)(4+) forms of the compounds were assigned on the basis of electrochemical and UV-vis spectroscopic data as having the electronic configuration sigma(2)pi(4)delta(2)pi(2) and sigma(2)pi(4)delta(2)pi(3)delta, respectively, and seemed to be independent of the isomer type ((3,1) or (4,0)). The spectral and electrochemical properties of the compounds both vary substantially as a function of the isomer type, but this is not reflected in the structural features of the compounds which are within the range of what is seen for other Ru(2)(5+) species described in the literature. The Ru-Ru bond lengths of the four structurally characterized (4,0) isomers of the ap complexes range from 2.275 to 2.296 A while those of the three structurally characterized (3,1) isomers of ap derivatives fall in the range 2.284-2.286 A and show no significant difference among the three compounds. The Ru-Cl bond lengths of the (3,1) isomers do not vary significantly with the bridging ligand and range from 2.458 to 2.471 A whereas those of the (4,0) isomers range from 2.437 to 2.487 A and show larger variations among the compounds. The Ru-Ru-Cl bond angle is virtually independent of the bridging ligand in the case of the (4,0) isomers but decreases with the electron-withdrawing effect of the substituent in the case of the (3,1) isomers.

Substituent and isomer effects on structural, spectroscopic, and electrochemical properties of dirhodium(III,II) complexes containing four identical unsymmetrical bridging ligands.

Substituent and isomer effects on the structural, spectroscopic, (UV-visible and ESR) and electrochemical properties of dirhodium(III,II) complexes containing four identical unsymmetrical bridging ligands are reported for seven related compounds of the type Rh(2)(L)(4)Cl where L = 2-(2-fluoroanilino)pyridinate (2-Fap), 2-(2,6-difluoroanilino)pyridinate (2,6-F(2)ap), 2-(2,4,6-trifluoroanilino)pyridinate (2,4,6-F(3)ap), or 2-(2,3,4,5,6-pentafluoroanilino)pyridinate (F(5)ap) anion. Rh(2)(2-Fap)(4)Cl exists only in a (4,0) isomeric conformation while Rh(2)(2,6-F(2)ap)(4)Cl, Rh(2)(2,4,6-F(3)ap)(4)Cl, and Rh(2)(F(5)ap)(4)Cl exist as both (4,0) and (3,1) isomers. It had earlier been demonstrated that Rh(2)(L)(4)Cl complexes can adopt different geometric conformations of the bridging ligands, but the current study provides the first example where two geometric isomers of Rh(2)(5+) complexes are obtained for one compound using the same synthetic procedure. The synthesis, structural, spectroscopic, and/or electrochemical properties of (3,1) Rh(2)(2,6-F(2)ap)(4)CN and (4,0) Rh(2)(2,4,6-F(3)ap)(4)(C triple bond C)(2)Si(CH(3))(3) are also reported and the data on these compounds is discussed in light of their parent complexes, (3,1) Rh(2)(2,6-F(2)ap)(4)Cl and (4,0) Rh(2)(2,4,6-F(3)ap)(4)Cl.

Synthesis and characterization of nitrosyl diruthenium complexes. Interaction between NO and CO across the metal-metal bond.

Two neutral diruthenium complexes and one anionic diruthenium complex, Ru2(dpf)4(NO), Ru2(dpf)4(NO)2, and [Ru2(dpf)4(NO)]-, where dpf is diphenylformamidinate anion, were synthesized and characterized as to their electrochemical and spectroscopic properties. Two of the compounds, Ru2(dpf)4(NO) and Ru2(dpf)4(NO)2, were also structurally characterized. Ru2(dpf)4(NO) undergoes reversible one-electron reductions under N2 at E1/2=0.06 and -1.24 V in CH2Cl2, 0.1 M TBABr. These processes are shifted to E1/2=0.18 and -0.78 V under CO due to the trans-coordination of a CO molecule which stabilizes the singly and doubly reduced forms of the metal-metal bonded complexes, thus leading to easier reductions. CO does not coordinate to Ru2(dpf)4(NO), but it does bind to the singly reduced species to generate [Ru2(dpf)4(NO)(CO)]- under a CO atmosphere in solution; characteristic NO and CO bands are seen for this compound at nuNO=1674 cm(-1) and nuCO=1954 cm(-1). Ru2(dpf)4(NO)2 displays a reversible one-electron reduction at E1/2=-1.24 V versus SCE and an irreversible reduction at Epc=-1.96 V in CH2Cl2, 0.1 M TBAP under N2. There are also two reversible one-electron oxidations at E1/2=0.24 and 1.15 V. Spectroelectrochemical monitoring of the Ru2(dpf)4(NO)2 oxidation processes in a thin-layer cell shows only a single NO vibration for each electrogenerated product and nuNO is located at 1726 (neutral), 1788 (singly oxidized), or 1834 (doubly oxidized) cm(-1). Finally, a labile CO complex, [Ru2(dpf)4(NO)(CO)]-, could be generated by passing CO into a solution of [Ru2(dpf)4(NO)]-. Formation of the mixed CO/NO adduct was confirmed by electrochemistry and infrared spectroscopy. Analysis of the NO and CO stretching vibration frequencies for [Ru2(dpf)4(NO)(CO)]- by in-situ FTIR spectroelectrochemistry and comparisons with data for Ru2(dpf)4(NO) and Ru2(dpf)4(CO) reveal the presence of a strong interaction between NO and CO across the Ru-Ru bond.

Solvent effects on the electrochemistry and spectroelectrochemistry of diruthenium complexes. Studies of Ru2(L)4Cl where L=2-CH3ap, 2-Fap, and 2,4,6-F3ap, and ap is the 2-anilinopyridinate anion.

Three Ru2(5+) diruthenium complexes, (4,0) Ru2(2-CH3ap)4Cl, (3,1) Ru2(2-Fap)4Cl, and (3,1) Ru2(2,4,6-F3ap)4Cl where ap is the 2-anilinopyridinate anion, were examined as to their electrochemical and spectroelectrochemical properties in five different nonaqueous solvents (CH2Cl2, THF, PhCN, DMF, and DMSO). Each compound undergoes a single one-electron metal-centered oxidation in THF, DMF, and DMSO and two one-electron metal-centered oxidations in CH2Cl2 and PhCN. The three diruthenium complexes also undergo two reductions in each solvent except for CH2Cl2, and these electrode processes are assigned as Ru2(5+/4+) and Ru2(4+/3+). Each neutral, singly reduced, and singly oxidized species was characterized by UV-vis thin-layer spectroelectrochemistry, and the data are discussed in terms of the most probable electronic configuration of the compound in solution. The three neutral complexes contain three unpaired electrons as indicated by magnetic susceptibility measurements using the Evans method (3.91-3.95 muB), and the electronic configuration is assigned as sigma2pi4delta2pi(*2)delta, independent of the solvent. The three singly oxidized compounds have two unpaired electrons in CD2Cl2, DMSO-d6, or CD3CN (2.65-3.03 muB), and the electronic configuration is here assigned as sigma2pi4delta2pi(*2). The singly reduced compound also has two unpaired electrons (2.70-2.80 muB) in all three solvents, consistent with the electronic configuration sigma2pi4delta2pi(*2)delta(*2) or sigma2pi4delta2pi(*3)delta*. Finally, the overall effect of solvent on the number of observed redox processes is discussed in terms of solvent binding, and several formation constants were calculated.

Electrochemical and spectroelectrochemical characterization of Ru(2)(4+) and Ru(2)(3+) complexes under a CO atmosphere.

Eleven different Ru(2)(4+) and Ru(2)(3+) derivatives are characterized by thin-layer FTIR and UV-visible spectroelectrochemistry under a CO atmosphere. These compounds, which were in-situ electrogenerated from substituted anilinopyridine complexes with a Ru(2)(5+) core, are represented as Ru(2)(L)(4)Cl where L = 2-CH(3)ap, ap, 2-Fap, 2,3-F(2)ap, 2,4-F(2)ap, 2,5-F(2)ap, 3,4-F(2)ap, 3,5-F(2)ap, 2,4,6-F(3)ap, or F(5)ap. The Ru(2)(5+) complexes do not axially bind CO while mono- and bis-CO axial adducts are formed for the Ru(2)(4+) and Ru(2)(3+) derivatives, respectively. Six of the eleven investigated compounds exist in a (4,0) isomeric form while five adopt a (3,1) geometric conformation. These two series of compounds thus provide a large enough number of derivatives to examine trends and differences in the spectroscopic data of the two types of isomers in their lower Ru(2)(4+) and Ru(2)(3+) oxidation states. UV-visible spectra of the Ru(2)(4+) derivatives and IR spectra of the Ru(2)(3+) complexes under CO are both isomer dependent, thus suggesting that these data can be used to reliably predict the isomeric form, i.e., (3,1) or (4,0), of diruthenium complexes containing four unsymmetrical substituted anilinopyridinate bridging ligands; this was confirmed by X-ray crystallographic data for seven compounds whose structures were available.