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The molecular structure of a series of newly developed ultraviolet (UV) curable electrical contact stabilization materials, which contain polyethylene glycol (PEG)-block-polypropylene glycol (PPG)-block-polyethylene glycol (PEG) capped with methacrylate functional groups on both ends as the reactive oligomers and a methacrylated PEG as the reactive diluent was studied in detail. The effects of reactive diluents, including functionalities and compositions were investigated via a combination of dynamic mechanical analysis, differential scanning calorimetry, FT-IR spectroscopy and wide angle X-ray diffraction. All the films exhibit completely amorphous state at room temperature regardless of the composition or thermal history. However, a small amount of PPPDI molecular chains undergo crystallization upon slow cooling. This crystallization is completely inhibited when mixed with di-functional reactive diluents, owing to the high cross-link density. The introduction of mono-functional reactive diluents restricts but not completely prevents the crystallization process, which causes the resulting films to be difficult to crystallize to lower crystallinity levels. On the other hand, adding non-reactive diluents transforms the resulting films to become a fast-crystallizing material, as a result of the low cross-link density and a large portion of unreacted oligomers along with the unreactive component. Additionally, the degree of heterogeneity for the cross-linked networks is generally increased by the addition of reactive diluents. The molecular structures of PEG-b-PPG-b-PEG dimethacrylate cross-linked networks as well as mixed with different types of reactive diluents at both room temperature and crystallizing temperature were proposed.

Paramagnetic resonance studies (EPR, ESEEM, ENDOR, and NMR) of a series of cobalt(II) bis-trispyrazolylmethane tetrafluoroborates are presented. The complexes studied include the parent, unsubstituted ligand (Tpm), two pyrazole-substituted derivatives (4Me and 3,5-diMe), and tris(1-pyrazolyl)ethane (Tpe), which includes a methyl group on the apical carbon atom. NMR and ENDOR establish the magnitude of 1H hyperfine couplings, while ESEEM provides information on the coordinated 14N. The data show that the pyrazole 3-position is more electron rich in the Tpm analogues, that the geometry about the apical atom influences the magnetic resonance, and that apical atom geometry appears more fixed in Tpm than in Tp. NMR and ENDOR establish that the BF4– counterion remains associated in fluid solution. In the case of the Tpm3,5Me complex, it appears to associate in solution, in the same position it occupies in the X-ray structure.

Half-hemiporphyrazine macrocycles, which can be called “semihemiporphyrazines”, were synthesized using the Re(CO)3 unit as a templating agent. The products of these template reactions are six-coordinate rhenium complexes, with a facial arrangement of carbonyls, a halide, and a bidentate semihemiporphyrazine chelate that tilts out of the plane of coordination. Three types of semihemiporphyrazines can be produced from these reactions, depending on the alternate heterocycle to the isoindoline unit; structures including pyridine, thiazole, and benzimidazole were formed. The electronic structures of these compounds were probed using spectroscopy as well as density functional theory methods.

Acetyl ferrocene and diacetyl ferrocene both readily react with an excess of hydrazine to afford the corresponding hydrazone compounds. These compounds can then be linked to Re(CO)3 via a metal-mediated Schiff base reaction, resulting in a series of ferrocene-Re(CO)3 conjugates with different stoichiometries. Conjugates with 1:1, 1:2, and 2:1 ferrocene: Re(CO)3 ratios can be produced via this "modular" type synthesis approach. Several examples of these conjugates were structurally characterized, and their spectroscopic, electrochemical, and spectroelectrochemical behaviors were investigated. The electronic structures of these compounds were also probed using DFT and TDDFT calculations.

A series of main chain organometallic polymers (MCOPs) containing Re(CO)3Cl(diimine) cores were synthesized. Three different types of polymerization reactions, including Yamamoto coupling, Heck coupling, and a new metal-mediated Schiff base formation/condensation reaction, allowed for the formation of metal polymers with 100% metal complex incorporation and average molecular weights (Mn) ranging from 25 to 850 kDa. Absorption spectroscopy, electrochemistry, and microscopy studies revealed that the type of polymerization effectively governs the physical and chemical properties of the target polymers. The electronic structures of monomeric and dimeric building units of these polymers backbones were probed by DFT and TDDFT computational methods. DFT calculations and electrochemical studies indicate that in all polymers the oxidation and reduction processes take place on Re(I) metal centers and polymer backbones, respectively. Incorporation of metal as an electron donor (D) and organic conjugated backbone as ...

We present the synthesis of several azadipyrromethenes with four peripheral arene units which can be readily generated via the well-established chalcone synthetic method. The stability and yields of these azadipyrromethenes is highly dependent on the nature of the arene substituent, with the bis-pyridine systems exhibiting the highest degree of instability. The structures of several of the compounds and their BF2 adducts are presented; intramolecular hydrogen bonding is observed in the free base ADPMs. We also present a study into the absorption and emission properties of the ADPMs and their BF2 adducts and observe that they are also highly dependent on the identity of the substituents.

Dimeric metal complexes can often exhibit coupling interactions via bridging ligands. In this report, we present two Re(CO)3 dimers, where the metals are linked via a bis(pyca) hydrazine (pyca = pyridine-2-carbaldehyde imine) Schiff base ligand. For the dimeric compounds 4 and 5, we observe strong coupling across the dimer as measured by cyclic voltammetry: ∼480 mV separations between the first and the second reduction waves that correspond to comproportionation constants close to 1.5 × 10(8). Evidence for a mixed valence state upon one electron reduction was also observed by spectroelectrochemistry in which a clear inter-valence charge-transfer (IVCT) band was observed in [4]- and [5]-complexes. The electronic structures of all target compounds were probed by DFT and TDDFT computational methods. DFT calculations indicate that reduction takes place at the diimine units, and that the observed coupling is a ligand-based phenomenon, rather than one that involves metal-based orbitals.

The Re(CO)3 unit was used to template the formation of aza(dibenzopyrro)methene (ADBM) in the presence of pyridine or N-methylimidazole. The products of these template reactions are six-coordinate complexes, with a facial arrangement of the carbonyls, a bidentate ADBM, and a sixth ligand (pyridine or N-methylimiadozle). Three types of ADBM ligands are produced from these reactions, depending on the degree of hydrolysis; bis(imine)-terminated, bis(oxo)-terminated, and mixed-imine/oxo chelates were formed.

Acetyl ferrocene and diacetyl ferrocene both readily react with an excess of hydrazine to afford the corresponding hydrazone compounds. These compounds can then be linked to Re(CO)3 via a metal-mediated Schiff base reaction, resulting in a series of ferrocene-Re(CO)3 conjugates with different stoichiometries. Conjugates with 1:1, 1:2, and 2:1 ferrocene: Re(CO)3 ratios can be produced via this “modular” type synthesis approach. Several examples of these conjugates were structurally characterized, and their spectroscopic, electrochemical, and spectroelectrochemical behaviors were investigated. The electronic structures of these compounds were also probed using DFT and TDDFT calculations.

A series of dimeric ReI(CO)3 compounds have been prepared by means of a one-pot reaction of [Re(CO)5X] (X = Cl, Br), pyridine-2-carboxyaldehyde, and o-, m-, or p-phenylenediamine. For the m- and p-substituted phenylenediamine reactions, phenyl-bridged bis(pyridine-2-carbaldimine) compounds of the formula [Re(CO)3X]2(μ-PPC) [3–7; X = Cl, Br; μ-PPC = m- or p-phenylene bis(pyridine-2-carbaldimine)] were produced, with m-phenylenediamine forming a mixture of isomers. For reactions with o-phenylenediamine, multiple products formed (compounds 8–11), which ranged from the desired o-phenylene bis(pyridine-2-carbaldimine) adduct to 2-pyridylbenzimidazole and bridging dipyridinylquinoxaline complexes. An example of each complex was structurally elucidated by single-crystal X-ray methods. The dimeric m- and p-phenylene-bridged Re(CO)3X compounds, including a sulfonate derivative designed to improve solubility, were investigated for possible photophysical applications through the use of UV/Vis spectroscopy and cyclic voltammetry; the study revealed coupling between the rhenium centers.

The new fluorescent chromophore BOPHY can be readily synthesized in two steps from commercially available reagents via the coupling of pyrrole-2-carboxaldehyde with hydrazine followed by reaction with BF3. The resultant symmetric and dimeric tetracycle is composed of two BF2 units in six-membered chelate rings appended with pyrrole units on the periphery. The quantum yields of fluorescence for the unmodified compound and the tetramethyl variant are near unity, with values of 95 and 92%, respectively, in CH2Cl2. We have probed the electronic structure of this compound via cyclic voltammetry and density functional theory analysis.

Half-hemiporphyrazine macrocycles, which can be called "semihemiporphyrazines", were synthesized using the Re(CO)

This research introduces the design of an adsorptive stripping voltammetric method for the cerium(III) determination at a carbon paste electrode, chemically modified with dipyridyl-functionalized nanoporous silica gel (DPNSG-CPE). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at −200 mV followed by the electrochemical detection of the Ce(III)/dipyridyl complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (1.0–28 ng mL−1). The precision for seven determinations of 4 and 10 ng mL−1 Ce(III) was 3.2% and 2.5% (relative standard deviation), respectively. The prepared electrode was used for the cerium determination in real samples and very good recovery results were obtained.

A new functionalized nanoporous silica gel with dipyridyl group (DPNSG) was synthesized. Then, the potentiometric response of the copper(II) ion was investigated at a carbon paste electrode chemically modified with this newly designed functionalized nanoporous silica gel. The electrodes with DPNSG proportions of 15.0% (w/w) demonstrated very stable potentials. Calibration plots with Nernstian slopes for Cu2+ were observed, 28.4 (+/-1.0) mV decade(-1), over a wide linear concentration range (1.0x10(-7) to 1.0x10(-2) M). The electrode exhibited a detection limit of 8.0x10(-8) M. Moreover, the selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode presented a response time of approximately 50s, high performance, high sensitivity in a wide range of cation activities and good long-term stability (more than 9 months). The method was satisfactory and was used to determine the copper ion concentration in waste waters, contaminated by this metal.

A new dipyridyl-functionalized silica gel (DPSG) was synthesized. The potentiometric response of silver ion was investigated at a carbon paste electrode chemically modified with functionalized nanoporous silica gel. The electrodes with a DPSG proportions of 10.1% (w/w), showed very stable potential. Calibration plots with Nernstian slopes for Ag+ were observed, 58.7 (±0.9) mV decade−1, over a wide linear range of concentration (5.0×10−7 to 1.0×10−1 M). The electrode has a detection limit of 1.0×10−7 M. The selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode has fast response time, high performance, high sensitivity in wide cation activity ranges, and good long term stability (more than 6 months). The method was satisfactory and used to determine the concentration of silver ion in waste waters contaminated by this metal.

Re(CO)3 conjugates 1 and 2 that incorporate azobenzenes can be readily generated via one-pot reactions using Schiff base reaction forming conditions. Excitation of the MLCT bands in 1 and 2 results in isomerization of the azobenzene moiety, and this process has been investigated.