The Role of Technical and Vocational Education in National Development

Education especially technical and vocational education is central to national development of fast developing countries such as the Asian Tigers In Africa and Nigeria in particular the adoption of technical and vocational education has not been given environmental recognition This paper argues that the acquisition of technical and vocational skills education system propelling self reliant development This paper seeks to understand the role of technical and vocational educations have in national development The paper examines the problems of technical and vocational education in Nigeri

Thiacalix[4]arene derivatives bearing imidazole units : a ditopic hard/soft receptor for Na⁺ and K⁺/Ag⁺ with an allosteric effect and a reusable extractant for dichromate anions

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Two novel receptors 5,11,17,23-tetra-tert-butyl-25,27-bis[(ethoxycarbonyl)methoxy]-26,28-bis-[1-methyl-(imidazole)meth-oxy] -2,8,14,20-tetra-thiacalix[4]arene (L1) and 5,11,17,23-tetra-tert-butyl-25,27-bis-[(benzyl)methoxy] -26,28-bis-[1-methyl-(imidazole)-methoxy]-2,8,14,20-tetrathiacalix[4] arene (L2) possessing imidazole moieties based on thiacalix[4]arene in the 1,3-alternate conformation have been synthesized and characterized. The crystal structures of L1 and L2 have been determined. The binding behaviour towards Li + , Na + , K + and Ag + ions has been examined by 1 H NMR titration experiments in (CDCl 3 /CD 3 CN; 10:1, v/v) solution. The exclusive formation of mononuclear complexes of L1 with metal cations is of particular interest revealing a negative allosteric effect in the thiacalix[4]arene family. Liquid-liquid extraction experiments indicate that synthesized L2 can be utilized as an efficient reusable extractant for dichromate anion by controlling the pH of the aqueous solution

Enhanced cytotoxicity of silver complexes bearing bidentate N-heterocyclic carbene ligands

A diverse library of cationic silver complexes bearing bis(N-heterocyclic carbene) ligands have been prepared which exhibit cytotoxicity comparable to cisplatin against the adenocarcinomas MCF7 and DLD1. Bidentate ligands show enhanced cytotoxicity over monodentate and macrocyclic ligands

1,3-Bis[(3-allyl­imidazol-3-ium-1-yl)meth­yl]benzene bis­(hexa­fluoridophosphate)

In the title compound, C20H24N4 2+·2PF6 −, the ethene and 3-allyl­imidazolium moieties of the cation are disordered over two positions with refined site occupancies of 0.664 (19):0.336 (19) and 0.784 (7):0.216 (7), respectively, whereas four F atoms of one hexa­fluoridophosphate anion and all atoms in the other hexa­fluoridophosphate anion are disordered over two positions with refined site occupancies of 0.764 (5):0.2365) and 0.847 (9):0.153 (9), respectively. The benzene ring is inclined at angles of 78.2 (3), 81.3 (4) and 73.9 (12)° with the 1H-imidazol-3-ium ring and the major and minor components of the disordered 1H-imidazol-3-ium ring, respectively. In the crystal, the hexa­fluoridophosphate anions link the cations into two-dimensional networks parallel to (001) via inter­molecular C—H⋯F hydrogen bonds. The crystal structure is further consolidated by π–π [centroid–centroid distance = 3.672 (3) Å] and C—H⋯π inter­actions

Synthesis, structures and photoluminescence properties of silver complexes of cyclic (alkyl)(amino)carbenes

Silver complexes of cyclic (alkyl)(amino)carbenes (CAACs), (RL)nAgX (n = 1, X = Cl, Br, I; n = 2, X = OTf; R = Me2, Et2, or adamantyl) are accessible in high yields by reacting free carbenes with silver salts. The smaller carbene ligand Me2L leads to the formation of a mixture of neutral (Me2L)AgCl and cationic [(Me2L)2Ag]+ products. The transmetallation of (AdL)AgCl with copper and gold halides gives the corresponding copper and gold compounds (AdL)MCl (M = Cu and Au) in a clean and quantitative reaction. Whereas (Me2L)AgCl is monomeric in the solid state, (Et2L)AgCl crystallizes as a Cl-bridged dimer. None of the compounds show metal-metal interactions. The complexes show blue photoluminescence, which consists of a fluorescence component with a lifetime of several nanoseconds, as well as a long-lived emission in the microsecond regime