Ionization of cyclic aromatic amines by free electron transfer: products are governed by molecule flexibility

The bimolecular electron transfer from secondary aromatic amines to parent radical cations of nonpolar solvents such as alkanes and alkyl chlorides results in the synchronous formation of amine radical cations as well as aminyl radicals, in comparable amounts. If as for cyclic aromatic amines (c-Ar(2)NH) the intramolecular bending motion around the amine group is restricted in varying degrees (acridane, phenothiazine) or completely prevented (carbazole), then this picture is modified. In the free electron transfer, the completely rigid carbazole yields exclusively amine radical cations. Acridane exhibits preferred radical cations, but phenothiazine with the more flexible six-membered ring involving sulfur as a further heteroatom follows the common two-product rule; see above. The phenomenon is reasoned by a peculiarity in the bimolecular free electron transfer where after diffusional approach the actual electron jump proceeds in the ultrashort time range. Therefore, it reflects femtosecond molecular motions which, in the case of free mobility, continuously pass through different molecule conformers, combined with fluctuation of the electrons of the responsible molecular n-orbitals. The rigid systems, however, do not show this effect because of a nonexistent bending motion.     

Bioaccumulation study of acrylates in algae (<Emphasis Type="Italic">Chlorella kessleri</Emphasis>) by Py-GC and Py-GC/MS

Acrylate monomers methylmethacrylate (MMA) and cyclohexylmethacrylate (CHMA) bioaccumulation has been determined in aquatic organism, algae (Chlorella kessleri). Algae were collected in amount of 0.4 mg and directly injected to the pyrolytical cell. In algae bodies accumulated monomers were analysed by pyrolysis gas chromatography (Py-GC) and pyrolysis gas chromatography coupled with mass spectrometry (Py-GC/MS). Traces of the accumulated monomers in algae body can be determined after 1-, 2-, 3-weeks of incubation. Maximum content of MMA was determined after 3-week of experiment, contrariwise in the case of CHMA after 2-week exposition. Relationship with pyrolysis temperature has also been studied.     

New Approaches to Coupling TLC with TOF-SIMS

JPC – Journal of Planar Chromatography – Modern TLC - A new hyphenated technique that enables coupling of thin-layer chromatography (TLC) with time-of-flight secondary-ion mass...     

Single-molecule magnets constructed from cyanometalates: {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Co, Ni)

Treatment of several divalent transition-metal trifluoromethanesulfonates [M(II)(OTf)2; M(II) = Mn, Co, Ni] with [NEt4][Tp*Fe(III)(CN)3] [Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] in DMF affords three isostructural rectangular clusters of {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Mn, 3; Co, 4; Ni, 5) stoichiometry. Magnetic studies of 3-5 indicate that the Tp*Fe(CN)3(-) centers are highly anisotropic and exhibit antiferromagnetic (3 and 4) and ferromagnetic (5) exchange to afford S = 4, 2, and 3 spin ground states, respectively. ac susceptibility measurements suggest that 4 and 5 exhibit incipient single-molecule magnetic behavior below 2 K.     

Pentafluorobenzaldehyde and its utilizing in organic synthesis

Over the past 50 years, pentafluorobenzaldehyde has received much attention due to its unique chemical and physical properties as well as its real or potential applications in chemistry of porphyrines, additives, drug delivery and in analytical chemistry. Pentafluorobenzaldehyde is multifunctional aromatic compound containing five atoms of fluorine and one aldehydic function. That is why it can provide nucleophilic substitutions of all or some atoms of fluorine, nucleophilic additions of aldehydic function, “haloform reaction” and some cyclization reactions. This year, it is being the 50th year, since the first synthesis of this compound was published.     

Mineralization of biomimetically carboxymethylated collagen fibrils in a model dual membrane diffusion system

In the present work, we show for the first time, that N^?-carboxymethyllysine is the major product of the in vitro non-enzymatic glycation reaction between fibrillar collagen and glucuronic acid. Dual diffusion membrane system was effectively used for oriented crystal growth of octacalcium phosphate/hydroxyapatite on the biomimetically carboxymethylated collagen fibrils. We hypothesize that the function of biomimetically carboxymethylated collagen is to increase the local concentration of corresponding ions in such a way that a critical nucleus of ions can be formed, leading to the formation of the mineral under specific micro-environment conditions achieved by using diffusion membrane system.     

On the number of Diophantine <Emphasis Type="Italic">m</Emphasis>-tuples

A set of m positive integers is called a Diophantine m-tuple if the product of any two of them is one less than a perfect square. It is known that there does not exist a Diophantine sextuple and that there are only finitely many Diophantine quintuples. On the other hand, there are infinitely many Diophantine m-tuples for m=2, 3 and 4. In this paper, we derive asymptotic estimates for the number of Diophantine pairs, triples and quadruples with elements less than given positive integer N. The author was supported by the Ministry of Science and Technology, Republic of Croatia, grants 0037110 and 037-0372781-2821.     

Y-type zeolites for the catalytic oxidative degradation of organic azo dyes in wastewater

Cobalt- and iron-containing catalysts active in the oxidation of organic dyes with hydrogen peroxide have been prepared from granular synthetic NaY and HY zeolites without a binder by ion exchange followed by heat treatment at 350–500°C. It has been demonstrated by X-ray photoelectron spectroscopy that cobalt and iron in these catalysts are in the form of Co²⁺ and Fe³⁺ ions on the support surface. The FeHY and CoNaY catalysts are most effective and stable in the oxidation of the anionic dye carmoisine in weakly acidic and alkaline media.     

The Last Fortress of Tin's Tyranny – Protodenitration of Nitroalkanes

Protodenitration, a direct reduction of nitroalkanes to corresponding alkanes, already spans two centuries and is enabled by various reagents. This mini-review provides a historical development of the fundamental transformation and highlights the governing position of the Ono-Tanner reaction employing tributyltin hydride. Due to the unchallenged dominance of the toxic tributyltin hydride and environmentally unpopular solvents sharply contrasting with modern ecological trends, the current situation was dubbed “the last fortress of tin's tyranny.”