1,721,027 research outputs found
Preparation of nano Arsenic(III) sulfide from arsenic(III)-dithiocarbamate precursors: Synthesis, spectral, single crystal X-ray structural, BVS and CSM analysis of tris(disubstituteddithiocarbamato)arsenic(III) complexes
No full textNano As2S3 was prepared solvothermally from three dithiocarbamte precursor complexes [As(chmdtc)3] (1), [As(chedtc)3] (2) and [As(dchdtc)3] (3) (where chmdtc = cyclohexylmethyldithiocarbamate, chedtc = cyclohexylethyldithiocarbamate and dchdtc = dicyclohexyldithiocarbamate). The nano arsenic trisulfide was characterized by PXRD, SEM-EDX, HRTEM-SAED techniques. The arsenic(III) complexes, (1), (2) and (3) were prepared and characterized by electronic, IR, TG/DTA and NMR (1H and 13C) spectra and single crystal X-ray diffraction. Electronic spectra of the complexes show signature bands in the range: 446–451 nm due to charge transfer transitions. Thioureide νC−N bands observed at 1444, 1468 and 1470 cm−1 for (1), (2) and (3) respectively indicate the partial double bonded nature. NMR spectra show that the immediate environment around thioureide nitrogen was largely affected by complex formation. 13C NMR confirmed the presence of thioureide carbon as a weak signal in the range: 197.63–198.32 ppm. The single crystal X-ray structures of [As(chmdtc)3] (1) [As(chedtc)3] (2) and [As(dchdtc)3] (3) indicate that the central atom is in a highly distorted octahedral environment of sulfur atoms due to the presence of lone pair of electrons. Continuous Shape measures of AsS6 cores in the three complexes are 7.5752, 6.2013 and 8.2473 for (1), (2) and (3) respectively confirm the proximate geometry to be octahedral. Complex (3) deviates to the largest extent from the octahedral geometry than the other two because of the largest steric demand of the two cyclohexyl rings. Two sets of As-S distances, shorter ones are in the range: 2.3164(7)–2.3438(8) Å and the longer ones are in the range: 2.841(2)–2.913(2) Å resulting in heteroleptic bonding. As a contrast to [As(chmdtc)3] (1), ethylcyclo- and dicyclo-analogues show non-covalent S—H, C—H and H—H short contacts, which results in supramolecular interactions. BVS calculations with structural data confirmed the formal oxidation state of arsenic as 3.0
Synthesis, spectral, cyclic voltammetric studies, and single crystal X-ray structure determination of the planar NiS2P2, NiS2PN, and NiS2PC chromophores
No full textSynthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4-MP)(2)](ClO4) (1), [Ni(dedtc)(4-MP)(NCS)](2), [Ni(dedtc)(PPh3)(NCS)] (3) and [Ni(dedtc)(PPh3)(CN)] (4) (dedtc = diethyldithiocarbamate, 4-MP = tri(4-iriethylphenyl)phosphine, PPh3 = triphenylphophine) are reported. IR spectra of complexes 1-4 show the characteristic thioureide (C-N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)2]. The d-d transitions are observed in the region 452-482 nm. The CV studies clearly show the presence of reduced electron density oil the nickel ions in mixed ligand complexes 14 compared to the parent dithiocarbamate. Single crystal X-ray, structure studies show all the complexes to containplanar NiS2P2, NiS2PN, and NiS2PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni-S distances are asymmetric. The thioureide C-N distance of the complexes 1-4 are less than the C-N distance observed in the parent [Ni(dedtc)(2)]
Steric and electronic effects of N-coordinated NC- and NCS- on NiS2PN: synthesis, spectral and single crystal X-ray structural studies on N,N'-di-n-butyldithiocarbamate complexes of nickel(II) with phosphorus and nitrogen donor ligands
No full textPlanar nickel(II) complexes involving N,N'-dibutyldithiocarbamate, such as [Ni(bu(2)dtc)(PPh(3))(NC)] (1) and [Ni(bu(2)dtc)(PPh(3))(NCS)] (2) (where bu(2)dtc N,N'-dibutyldithiocarbamate anion) have been prepared, characterized by electronic, IR and NMR spectra and their structures determined by single crystal X-ray crystallography. Cyclic voltammetric characterizations of the complexes are also reported. IR spectra of the two complexes indicate the isobidentate coordination (nu(c-s) similar or equal to 1095 cm(-1) without splitting) of the dithiocarbamate moiety. The important stretching mode characteristic of the thioureide bond (nu(C-N)) occurs at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(bu(2)dtc) 2]. The electronic spectra of 1 and 2 show signature bands at 426 nm and 478 nm, respectively. NMR spectra show large (31)P chemical shifts in both compounds and the most important N(13)CS(2) chemical shift appears at 204.86 ppm and 203.23 ppm for 1 and 2, respectively. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed-ligand complexes 1 and 2 compared to the parent dithiocarbamate. Single crystal X-ray structure studies show that 2 crystallizes as a new triclinic polymorph, whose molecular structure closely resembles that of the previously reported monoclinic form. Both complexes contain a planar NiS(2)PN chromophore in keeping with the observed diamagnetism. In both complexes the Ni-S distances are significantly different. The thioureide C-N distances of the complexes are shorter than those observed in the parent [Ni(bu(2)dtc)(2)]. The two compounds allow comparison of the influence of NCS-in place of NC(-)
Quantification of distortions associated with planar NiS4, NiS2NP and NiS2P2 chromophores: Synthesis, structural and CSM analysis
No full textPlanar, diamagnetic [Ni(dadtc)(PPh 3 )(NCS)] (1), [Ni(dadtc)(PPh 3 ) 2 ]ClO 4 (2) and [Ni(dadtc)(dppb)]ClO 4 (3) (where dadtc = diallyldithiocarbamate, PPh 3 = triphenyl phosphine, NCS = thiocyanate and dppb = (1,4-bis(diphenylphosphino)butane) have been synthesized and characterized by UV–vis, IR, 1 H, 13 C, 31 P NMR, CV, and thermal analysis. Solvothermal decomposition of the compounds yielded NiS. 1 H NMR signals showed the a -CH 2 protons to be the highly deshielded and 13 C NMR spectra showed the characteristic thioureide (N 13 CS 2 ) carbon signals around 200 ppm. 31 P chemical shifts showed the following order:
(2) (29.4 ppm) > (3) (22.40 ppm) > (1) (12.7 ppm). Single crystal X-ray analysis of (1), (2) and (3) showed
a distorted square planar coordination in the NiS 2 NP and NiS 2 P 2 chromophores. Deviation of the chromophore from square planar geometry towards tetrahedral geometry has been assessed for the first time
by Continuous Symmetry Measure calculation in a scale of ‘0’ to ‘100’, which showed the following
decreasing order from planarity: NiS 4 (0.894) ? NiS 2 P 2 (0.660) > NiS 2 NP (0.615) > NiS 2 P 2 (chelating
dppb) (0.411). The CSM analysis reveals that the deviation from planarity is less than unity for all the
chromophores. However, NiS 2 P 2 (chelating dppb) shows relatively the lowest deviation indicating chelate
induced stability
cobalt sulfide from tris (cyclohexylpiperazinedithiocarbamato)cobalt(III) and characterization, single crystal X-ray crystal structure of the precursor
No full textSolvothermal formation of CoS nano particles is reported with a cobalt(III) dithiocarbamate as a single source precursor. Morphology and composition of the nano product have been characterized by PXRD and EDX analysis. Four unsymmetrically substituted tris cobalt(III) compounds, [Co(chmdtc)3] (1), [Co(chedtc)3] (2), [Co(achdtc)3] (3), and [Co(chpdtc)3] (4) (where chmdtc = cyclohexylmethylcarbodithioate, chedtc = cyclohexylethylcarbodithioate, achdtc = allylcyclohexylcarbodithioate and chpdtc = cyclohexylpiperazinecarbodithioate) were synthesized and characterized. Compounds (1)– (4) show bands at 634, 642, 635, and 643 nm respectively, due to d-d transitions. One electron quasi reversible reductions due to Co(III)/Co(II) redox process are observed in CV. In the 13C NMR spectra of the complexes, the thioureide (N13CS2) carbons resonate between 203.8 and 205.7 ppm. The observed deshielding of the –CH2 protons in 1H NMR of the compounds is attributed to the shift of electron density on the sulfur (or the metal) through the thioureide π system. TGA supported the proposed formulas of the compounds. Single crystal X-ray structure of [Co(chpdtc)3] (4) shows that the cobalt is in a distorted octahedral environment. Bond Valence Sum (BVS) calculations confirmed the formal oxidation state of cobalt as +3
Bis(μ-N-benzyl-N-methyldithiocarbamato)-1:2κ3S,S′:S′;1:2κ3S:S,S′-bis[bis(N-benzyl-N-methyldithiocarbamato-κ2S,S′)thallium(III)]
No full textThe molecule of the dinuclear title compound, [Tl2(C9H10NS2)6], possesses a crystallographically imposed centre of symmetry. Each TlIII atom is seven-coordinated by S atoms of four different dithiocarbamate anions in a distorted pentagonal-bipyramidal coordination geometry. The crystal structure is stabilized by a C—H...S hydrogen-bond interaction linking complex molecules into chains running parallel to the b axis. Intramolecular C—H...S hydrogen bonds are also present
Synthesis, structure, optical, and thermal properties of diallylammonium hexabromostannate(IV) hybrid
No full text Diallylammonium hexabromostannate(IV) was synthesized and characterized by IR, 1H,13C NMR, DRS, TG-DTA, Single crystal XRD. 1H chemical shifts of the protons in the hybrid are lower than the diallylammonium cation due to extensive hydrogen bonded and weak van der Waals interactions. The NH2+ protons of the hybrid are observed as a singlet at 8.963 ppm compared to those of the diallylammonium chloride at 9.800 ppm, a significant decrease. 13C NMR spectrum shows a maximum downward chemical shift for α-C(H2). DRS spectrum shows a strong charge transfer transition in the range 429 to 492 nm. The hybrid is thermally stable up to ∼195°C. Single crystal X-ray crystallography shows the asymmetric unit to be [C6H12N]+ 0.5[SnBr6]2−. All the bromide ions are involved in hydrogen bonding. BVS of tin in diallylammonium hexabromostannate(IV) was calculated based on the Sn-Br bond distances obtained from the single crystal X-ray structural analysis as 3.941, which is close to its formal oxidation state of +4. This is the first report which clearly established the formal oxidation state of tin in a hybrid material from X-ray structural data. The CSM of SnBr62− anion was found to be 0.0145 indicating its near perfect octahedral geometry.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
