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The synthesis and magnetostructural analysis of 2-(4,5,6,7-tetrafluorobenzidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1-H-imidazole-3-oxide-1-oxyl (F4BImNN) are described. Magnetic and calorimetric studies have shown that it has acted as a quasi one-dimensional (1D) organic ferromagnet whose FM coupled, hydrogen-bonded chains are antiferromagnetically coupled to give magnetic ordering below the critical temperature.

Model 1,4-bis(styryl)benzene derivatives related to poly(2-bromo-5-methoxy-1,4-phenylenevinylene) are synthesized to probe the effect of bromination on excited-state behavior of conjugated phenylenevinylene analogues. Solution absorption maxima at about 385 nm, without evidence of excimer formation up to 100 mu M are seen.

The crystallography and magnetic behavior of two coordination complexes formed between manganese(II) hexafluoroacetylacetonate/copper(II) hexafluoroacetylacetonate and the conjugated radical 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine (PyrimPh-NIT) is presented. The same head-to-head cyclic dimer connectivity is present in both complexes despite the geometric differences.

The aggregation number of a nonionic surfactant micelle, Triton X 100 (TX100), in aqueous solution is determined as function of pressure by using the method of steady-state fluorescence quenching. It is found that with increasing pressure, the aggregation number of TX100 takes a minimum.

Heat capacities of the organic free radical magnet 2-tert-butylaminoxylbenzimidazole (BABI) are measured in the 0.2-300 K range by adiabatic calorimetry. The magnetic properties of BABI are investigated from a thermodynamic viewpoint and an antiferromagnetic phase transition is observed at T(sudphysical chb N) = 1.7 K.

Interactive visualization of infrared spectral data is discussed relative to learning about spectroscopy and to synergy of computation, visualization, and experimentation for second-year chemistry students. An interactive dual-display format has been used for a more dynamic, student-controllable environment. Software used is described and programming and file structure discussed.

ESR spectroscopy studies of products derived from cryogenic matrix photolysis of 2,4,6-triazopyridines are presented.

ESR and UV investigation of synthesized diradical reveals its lifespan that extends to weeks even with the existence of oxygen. It is also found to be capable of surviving brief heating in toluene of up to about 60 degrees celsius. In a temperature that ranges from -10 to 50 degrees celsius, the diradical exhibited reversible thermochromic behavior. Meanwhile, the phenoxyl and nitroxide spin carrying units almost exhibited an isolated behavior when subjected under hyperfine analysis.

A study was conducted to determine the reactivity and electron paramagnetic resonance spectroscopy of 2-biphenylenylcarbene. Carbene 1 seemed a to be a normal arylcarbene from most indications since its reactivity approximates that of phenylcarbene. Its zfs parameters, however, indicate a slightly more delocalization compared to the naphthylcarbenes. Results also revealed the singlet to be the reactive spin state.

Thermally stable but light sensitive diazides were synthesized and subsequently subjected to photolysis to yield quininoidal dinitrenes. The dinitrenes were characterized by electron spin resonance spectrometry (ESR) and the molecules were found to exhibit triplet ESR. Such observation was proposed to be due to their excited states. The dinitrenes also had large zero field splitting (zfs) values which were found to be in accordance with spin polarization models. These findings would be valuable for further studies on the exchange interaction between unpaired electrons.

Ferromagnetic interaction of poly(phenylenevinylene)-attached phenoxyl radicals in the presence of a palladium catalyst was investigated by electron spin resonance and measurement of the magnetic properties with a SQUID magnetometer. EPR spectra and force field calculations indicated intramolecular and through-bond interactions between pendant unpaired electrons for the polyradicals through planarized and pi-conjugated skeletons.

The unimolecular generation of phenoxyl-based radicals using aryloxy oxalyl chlorides (AOCs), aryloxy oxalyl tert-butyl peroxides (AOBs) and diaryl oxalates (DAOs) is described. The results showed the usability of AOCs for photochemical generation of phenoxyl radicals but are only stable as precursors when 2,6-ditert-butylated derivatives are used. AOBs produce phenoxyl radicals more readily than DAOs but DAOs have fewer side reactions.

A transition intermediate state of the form pentamethylenepropane (PMP) is obtained by the isomerization of the 2,4-dibenzylidene-bicyclo(3.1.0)hexan- 3-one at the cyclopropyl ring. Computational analysis of the bicyclic PMP derivatives 1,2,3-trimethylenecyclohexane-4,6-diyl and 2,6-dimethylene- cyclohexanone-3,5-diyl indicates that they have 3B2 ground states which are less than 2 kcal/mol compared to their corresponding diradical 1A1 states.

Photolysis of diazides in degassed 2-methyltetrahydrofuran at 77K produces various bis carbylnitrenes linked by heterocyclic pseudoaromatic rings. Linkers 2, 5-furandiyl, 2,5-thiophenediyl and 2,5-pyrrolediyl connect the 3-nitrenophenyl and 4-nitrenophenyl groups, yielding different dinitrenes. Few dinitrenes exhibit quintet ESR spectra and have pseudodisjoint ground state singlet dinitrene and a thermally populated excited quintet state. Few dinitrenes show triplet biradical ESR spectra. The biradical intensity decreases with decreasing temperature, indicating the dinitrenes to be ground state single biradicals.

Semiempirical MO-CI methods enable qualitative determination of ground state spin multiplicities of various stilbenoid diradicals. Substitution of methylene radical sites with heteroatom spin-bearing sites has no influence on ground state multiplicities while nitroxide substitution reduces magnetic interactions. Analysis of the magnetic properties of stilbenebis(N-tert-butyl nitroxide) reveals the higher stabilities of the m,m'- and m,p'-isomers compares to that of the o,m'-isomer.

The cryogenic matrix photolysis of diazide precursors that were expected to produce biphenyl-3,4'-dinitrene (1), biphenyl-3,3'-dinitrene (2) and biphenyl-4,4'-dinitrene (3), was used to analyze the major influence of connectivity on the nature of intramolecular exchange coupling of unpaired electrons by the biphenyl group. The findings related to dinitrenes 1 to 3, when compared with those connected with dicarbene molecules, revealed that the electron exchange coupling patterns of dinitrenes and dicarbenes are similar.

A study is made on the electronic structure-property relationships of organic pi-conjugated non-Kekule molecules. This endeavor is prompted by theories stating that organic materials might be designed by rational design strategies that are based on qualitative principles. The results indicate that dinitrenes coupled by conjugated linking groups, are useful in assessing the qualitative relationships between structure and exchange coupling in organic open-shell systems.

Ab initio studies, using sigma-S pi-SDCI optimization, reveal why m-quinone should exist as a triplet in the ground state. The behavior of m-quinone differs from that of 2,4-cyclobutadiene in the that latter changes from a triplet to a singlet ingoing from a dimethylene to a dioxo species. Based on a lower triplet energy value compared to the lowest singlet energy, the study notes that the lowest singlet state of m-quinone exhibits little pi-bonding between the exocyclic CH2and the ring, in contrast to that of 2,4-dimethylcyclobutane. This difference explains the inability of methylene- oxygen substitution to change m-quinone from a triplet to a singlet.

The Wittig half-reaction of the unstabilized ylides H3P=CH-CH3 and (C6H5)3P=CH-CH3 with aldehydes is examined using MNDO-PM3 molecular orbital methodology to assess the one-step cycloaddition mechanisms suggested by Schlosser and Vedejs. The model reactions involve the ylides ethylidenephosphorane and ethylidenetriphenylphosphorane with acetaldehyde, propargylaldehyde and glyoxylonitrile to give the Z and E oxaphosphetanes, respectively.

Summary: This contribution investigates the utilization of carboxylic acid and hydroxyl functionalized single wall carbon nanotubes (SWNTs) for enhancing thermoelectric (TE) performances of the composites prepared with an inherently conductive polymer, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Our results indicated an atypical thermoelectric property which is a simultaneous increase in electrical conductivity and the Seebeck coefficient which leads a greater power factor (PF) up to 22 μW m−1 K−2 while it is only 0.7 μW m−1 K−2 for the sample prepared with pristine SWNT. The functionalities on the carbon nanotube walls facilitate blend dispersion in aqueous media without requiring any surfactants and also enhance PFs as a result of improved charge transport routes. The improvement in the thermoelectric performance can be ascribed to hydrogen bonds with the ‐COOH or ‐OH groups on the nanotube walls which help induce the polymer chains to adopt an extended conformation. [ABSTRACT FROM AUTHOR]

Triplet 2-(dicyclopropylmethylidene)cyclopentane-1,3-diyl, CP2TMM, from the azo compound precursor derived from 6,6-dicyclopropylfulvene which resembles the 6,6-dimethyl species is described. Conformational possibilities were examined using ab initio calculations. Results show that triplet CP2TMM hyperfine splitting is consistent with conformation B. It was found that the most stable conformation of each spin state is a C2-symmetric structure providing a 10 kcal/mol singlet-triplet energy gap favoring the triplet.