Cyanocobalt(III) complexes of penta- and tetradentate-coordinated macrocyclic hexaamines

The pendent-arm macrocyclic hexaamine trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine (L) may coordinate in tetra-, penta- or hexadentate modes, depending on the metal ion and the synthetic procedure. We report here the crystal structures of two pseudo-octahedral cobalt(III) complexes of L, namely sodium trans-cyano(trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)cobalt(III) triperchlorate, Na[Co(CN)(C13H30N6)](ClO4)(3) or Na{trans-[CoL(CN)]}(ClO4)(3), (I), where L is coordinated as a pentadentate ligand, and trans-dicyano(trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) cobalt (III) trans-dicyano (trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diaminium)cobalt(III) tetraperchlorate tetrahydrate, [Co(CN)(2)(Cl4H32N6)][Co(CN)(2)(Cl4H30N6)](ClO4)(4)•-4H(2)O or trans-[CoL(CN)(2)]trans-[Co(H2L)(CN)(2)] (ClO4)(4)•-4H(2)O, (II), where the ligand binds in a tetradentate mode, with the remaining coordination sites being filled by C-bound cyano ligands. In (I), the secondary amine Co-N bond lengths lie within the range 1.944 (3)-1.969 (3) &ANGS;, while the trans influence of the cyano ligand lengthens the Co-N bond length of the coordinated primary amine [Co-N = 1.986 (3) &ANGS;]. The Co-CN bond length is 1.899 (3) &ANGS;. The complex cations in (11) are each located on centres of symmetry. The Co-N bond lengths in both cations are somewhat longer than in (I) and span a narrow range [1.972 (3)-1.982 (3) &ANGS;]. The two independent Co-CN bond lengths are similar [1.918 (4) and 1.926 (4) &ANGS;] but significantly longer than in the structure of (1), again a consequence of the trans influence of each cyano ligand

Lanthanide appended rotaxanes respond to changing chloride concentration

Lanthanide appended rotaxanes have been prepared by the CuAAC ‘click’ reaction between an azide appended rotaxane and lanthanide complexes of propargyl DO3A. The resulting complexes are luminescent, and exhibit chloride responsive luminescence behavior consistent with the existence of two independent halide binding pockets, one in the rotaxane cavity and one on the ninth (axial) coordination site of the lanthanide. Strong halide binding to europium gives rise to changes in the relative intensity of the hypersensitive ΔJ = 2 transition compared to the rest of the europium emission spectrum, combined with quenching of the overall intensity of emission as a consequence of non-radiative quenching by the bound halide. The weaker interaction with the rotaxane pocket mediates a subsequent recovery of intensity of the europium centered luminescence despite the considerable separation between the lanthanide and the rotaxane binding pocket

Immobilisation of electroactive macrocyclic complexes within titania films

The 4-carboxyphenyl-appended macrocyclic ligand trans-6,13-dimethyl-6-((4-carboxybenzyl)amino)-1,4,8,11-tetraazacyclotetradecane-6-amine (HL10) has been synthesised and complexed with Co-III. The mononuclear complexes [Co(HL10)(CN)](2+) and [CoL10(OH)](+) have been prepared and the crystal structures of their perchlorate salts are presented, where the ligand is bound in a pentadentate mode in each case while the 4-carboxybenzyl-substituted pendent amine remains free from the metal. The cyano-bridged dinuclear complex [CoL10-mu-NC-Fe(CN)(5)](2-) was also prepared and chemisorbed on titania-coated ITO conducting glass. The adsorbed complex is electrochemically active and cyclic voltammetry of the modified ITO working electrode in both water and MeCN solution was undertaken with simultaneous optical spectroscopy. This experiment demonstrates that reversible electrochemical oxidation of the Fe-II centre is coupled with rapid changes in the optical absorbance of the film

Sixty years young: The diverse biological activities of metal polypyridyl complexes pioneered by Francis P Dwyer

Sixty years ago, the Australian chemist Francis P. Dwyer pioneered the use of ruthenium polypyridyl complexes as biologically active compounds. These chemically inert and configurationally stable complexes revealed an astonishing range of interesting biological activities, such as the inhibition of the enzyme acetylcholinesterase, anti-cancer activity in vivo, and bacteriostatic/ bacteriocidal action. This review commemorates the sixtieth anniversary of Dwyer and co-workers' landmark 1952 publication, summarises their broader achievements in biological inorganic chemistry, and discusses the contribution of this work to the development of modern biological and medicinal inorganic chemistry. 漏 2012 CSIRO

Phosphine Complexes of an Enantiomerically Pure, Atropisomeric Arsenium Ion

The first enantiomerically pure secondary iodoarsine has been prepared by ring closure of (a<i>R</i>)-[{Li­(TMEDA)}₂{2,2′-bis­(methylene)-1,1′-binaphthylyl}] with dichlorophenylarsine, followed by disproportionation of the resulting seven-membered (a<i>R</i>)-phenylarsepine with triiodoarsine in boiling toluene. The corresponding (a<i>R</i>)-chloroarsepine was prepared from the (a<i>R</i>)-iodoarsepine by halide metathesis with silver chloride in dichloromethane. The crystal structures of the two air-stable (a<i>R</i>)-haloarsepines have been determined. A series of phosphine-stabilized arsenium hexafluorophosphates has been prepared from the (a<i>R</i>)-iodoarsepine by reactions with trimethylphosphine, dimethylphenylphosphine, and [2-(methoxymethyl)­phenyl]­dimethylphosphine in dichloromethane in the presence of aqueous potassium hexafluorophosphate. The crystal structures of the three complexes have been determined. The structure in each case revealed the significant twist in the (a<i>R</i>)-binaphthyl framework of the seven-membered arsepinenium ion and the coordination of the phosphine approximately orthogonal to the trigonal AsC₂ plane of the arsepinenium ion. The ¹H­{³¹P} NMR spectrum of the dimethylphenylphosphine complex in dichloromethane-<i>d</i>₂ at 25 °C contains broadened singlets for the diastereotopic P<i>Me</i> groups and a multiplet for the methylene protons of the arsepinenium ring because of phosphine exchange. At the slow exchange limit (ca. −50 °C), the complex cation is devoid of symmetry, as indicated in the ¹H NMR spectrum by the sharp resonances for the P<i>Me</i> groups and separate AB and A′B′ spin systems for the two pairs of methylene groups in the arsepinenium ring. The ¹H­{³¹P} NMR spectrum of the closely related [2-(methoxymethyl)­phenyl]­dimethylphosphine–arsenium complex in dichloromethane-<i>d</i>₂ at 25 °C is sharp, however, which is in agreement with additional stabilization of the complex by coordination of the 2-methoxymethyl group to the phosphorus and arsenic atoms, as indicated in the crystal structure. The resolution of (±)-[2-(methoxymethyl)­phenyl]­methyl­(2-naphthyl)­phosphine was achieved by complexation to the enantiomerically pure (a<i>R</i>)-arsenium hexafluorophosphate auxiliary. The crystal structure of the less soluble a<i>R</i>,<i>R</i>_P diastereomer of the phosphine–arsenium complex confirmed the absolute configuration of the resolved <i>P</i>-chiral phosphine

Mobile Phone-based Colorimetric Detection of Perfluorocarboxylic Acids using Porphyrin Hosts

Perfluorinated carboxylic acids (PFCAs) are widespread, potentially harmful, and difficult to detect pollutants. Here we investigate the use of three colorimetric porphyrin host molecules with chain lengths derived from different PFCA precursors as visual sensors for a range of different sized perfluorocarboxylates. We found that modifications to the length of the fluorinated chains led to subtleties in binding preferences and the resultant colorimetric (RGB) response. Host-guest interactions were investigated with UV-visible spectroscopy, and ImageJ software analysis was used to relate RGB information from digital photographs with binding and perceived colors. The CIE76 formula for color difference was used for the visual estimation of PFCA concentrations from generated color charts. Color responses were also parameterized to generate calibration curves from known concentrations of perfluorooctanoic acid so that total PFCA concentrations could be estimated with less than 20% error using a phone camera across a 10 ppb (parts per billion) – 16 ppm (parts per million) range

3D Printed Micrometer-Scale Polymer Mounts for Single Crystal Analysis

3D printed micrometer-scale polymer mounts for single crystal analysis have been prepared by photopolymerization using digital light projection stereolithography (DLP-SLA), with a commercially available digital light projection stereolithography printer (US$4000) and 3DM-ABS resin (US$150 per liter). The polymer mounts were prepared in batches of 49 in 1 h 15 min, which allowed for rapid prototyping and testing of new crystal mounting designs, with a resin cost of 0.2¢ US per mount. The suitability of the 3D printed mounts for single crystal crystallography has been demonstrated through their use in Cu Kα X-ray diffraction experiments of Rochelle salt (sodium potassium tartrate), the protein lysozyme, and has been employed for routine crystallographic analysis of organic and inorganic materials

Arbutin Derivatives Isolated from Ancient Proteaceae: Potential Phytochemical Markers Present in Bellendena, Cenarrhenes, and Persoonia Genera

Extensive phytochemical studies of the paleoendemic Tasmanian Proteaceae species Bellendena montana, Cenarrhenes nitida, and Persoonia gunnii were conducted employing pressurized hot water extraction. As part of these studies, six novel glycosides were isolated, including rare examples of glycoside-containing natural products featuring tiglic acid esters. These polar molecules may represent potential phytochemical markers in ancient Proteaceae