Search

Examples of photoluminescence (PL) are being reported with increasing frequency in a wide range of organisms from diverse ecosystems. However, the chemical basis of this PL remains poorly defined, and our understanding of its potential ecological function is still superficial. Among mammals, recent analyses have identified free‐base porphyrins as the compounds responsible for the reddish ultraviolet‐induced photoluminescence (UV‐PL) observed in the pelage of springhares and hedgehogs. However, the localization of the pigments within the hair largely remains to be determined. Here, we use photoluminescence multispectral imaging emission and excitation spectroscopy to detect, map, and characterize porphyrinic compounds in skin appendages in situ. We also document new cases of mammalian UV‐PL caused by free‐base porphyrins in distantly related species. Spatial distribution of the UV‐PL is strongly suggestive of an endogenous origin of the porphyrinic compounds. We argue that reddish UV‐PL is predominantly observed in crepuscular and nocturnal mammals because porphyrins are photodegradable. Consequently, this phenomenon may not have a specific function in intra‐ or interspecific communication but rather represents a byproduct of potentially widespread physiological processes. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a new series of relatively flexible cofacial donor-acceptor dyads for singlet-singlet energy transfer with the corrole or etio-porphyrin free base and zinc porphyrin is described, as the acceptor and donor. The results show that the presence of a bulky group located between the acceptor and the donor moiety influences the energy transfer rate.

The formation of a [pi]-complex of a free-base bisporphyrin (H4DPOx) with acridinium perchlorate (Ac[H.sup.}Cl[O4.sup.-]) and the photodynamics in benzonitrile (PhCN) is reported. Results reveal that a 1:1 [pi]-complex is formed between H4DPOx and Ac[H.sup.} in PhCN with a large binding constant.

The synthesis of bisporphyrins and estimation of the efficient surface of the chromophores for O(sub 2) interactions are presented. It is concluded that there is a diffusion mechanism of O(sub 2) towards the chromophore contrasting with a static mechanism and it is possible for the preparation of effective O(sub 2) sensing porphyrins at an extreme price.

A combination of potentiometric and absorption spectroscopic data allowed to characterize the formation and the dissociation mechanism of octacoordinated lead complexes of primary and tertiary tetrakiscarbamoylmethyl cyclam derivatives. In solution, the Pb(super 2+) cation is entrapped in a molecular cage constituted by the four macrocyclic nitrogen and the four amidic oxygen atoms.

The selectivity of the reaction of two linear tetraamines with pyruvic aldehyde, the cyclization of the bisaminal intermediates with biselectrophilic reagents, and the quaternization of the protected macrocycles are discussed. The structure of the compounds was solved by X-ray diffraction, and the unexpected results are rationalized according to the molecular modeling calculations.

The synthesis of a novel family of heterobinuclear cofacial biphenylene (B), anthracene (A), 9,9-dimethylxanthene (X) or dibenzofuran (O) bridged porphyrin-corrole complexes, (PCY)MCICoCl, is reported, M being either an iron(III) or manganese(III) ion. Each complex is characterized by electrochemistry, mass spectrometry, UV-vis, IR, and electron spin resonance spectroscopy.

A study was carried out on the free base and biszinc(II) complexes of 5,17-bis[5(2,8,13,28-tetramethy-porphyrin0]-25,26,27,28-tetrapropoxycalix[4]arene that was obtained in four and five steps respectively. Details of the photophysical data and variable-temperature (super 1)H NMR that shows an open geometry of the two porphyrin macrocyles at 298 K are discussed.

The synthesis and characterization of cofacial copper biscorroles and porphyrin-corroles linked by a biphenylenyl or anthracenyl spacer are described. The comparative study of four cofacial copper bis-corrole) BC and porphyrin-corrole (PC) dyads and their related monomeric corrole and porphyrin units shows that electron interaction between the two face-to-face macrocycles of these cofacial derivatives depends critically on the type and size of rigid spacer.

The copper(II) binding properties of the macrobicyclic diamide 1,9,12,18,22-pentaazatricyclo[7.6.6.1(super 3,7)]docosa-3,5,7-(22)-triene-13,19-dione (L(super 1)) are investigated by spectroscopic, structural, thermodynamic and electrochemical methods. Cross-bridging the 1 and 8 position of 5,12-dioxocyclam with a 2,6-pyridyl group affords a hemispherical macrobicyclic ligand exhibiting a split personality.