Amany M.A. Ibrahim

Construction of supramolecular copper architecture via tetrahedral Cu(CN)4 building blocks and trigonal bipyramidal [R3Sn] connecting units

Abstract The self assembly of the pyramidal tetrahedral Cu(CN)4 building blocks, the trigonal bipyramidal [R3Sn] connecting units and the guest–template–cations leads to the construction of new types of non-interpenetrating polymeric networks. Twelve polymers have been prepared, most of them, according to the desired stoichiometry while polymers 9–12 represent binuclear copper compounds. These polymers are formed when no suitable space-demanding alkyl groups are used. The structures of the polymers under investigation were confirmed by elemental analysis, IR and Raman spectra, thermal analysis and NMR spectroscopy.

Supramolecular host–guest coordination systems: [(G+)(Me3E)3MII(CN)6]∞ as ion exchangers, where (G+=Me3E, Et4N or stp), (E=Sn or Pb) and (M=Fe or Ru)

Abstract A number of 3D-coordination polymers, constructed via [ d M(CN) 6 ] building blocks and (Me 3 E) connecting units, have been prepared and characterized by X-ray powder diffraction and different spectroscopic methods. 1-Methyl-4-(4′- R -styryl) or (2′- R -styryl) pyridinium cations (stp) have been successfully encapsulated within the expandable wide channels of the 3D-coordination polymers by tribochemical or ion exchange reactions producing novel molecular composites. Apart from 6 , [(4′-OCH 3 -stp)(Me 3 Sn) 3 Fe II (CN) 6 –MeOH] ∞ which exhibits thermochromic behaviour, the molecular composites [(stp) x (Me 3 E) 3 Fe III 1– x Fe II x (CN) 6 ] ∞ , 1 – 12 are mixed valence materials exhibiting localized interaction between the mixed valence iron. The results indicated an ion charge transfer interaction between the guest stp-cations and the host matrix. The molecular composites [(stp)(Me 3 E) 3 M II (CN) 6 ] ∞ , 13 – 18 are due to the facile readiness of the coordination polymers [(Me 3 E) 4 M(CN) 6 ] ∞ and [(Et 4 N)(Me 3 Sn) 3 Fe(CN 6 )] ∞ to ion exchange.

Charge transfer complexes of some thiazoles and benzothiazoles with certain nitrobenzene derivatives

Abstract Interaction of some thiazole and benzothiazole derivatives as donors with certain di- and trinitrobenzene derivatives as acceptors results in the formation of 1:1 molecular species. The infrared, NMR and ultraviolet analysis of the complexes with non-acidic acceptors reveals the presence of π-π* interaction from a HOMO of the thiazole nucleus or the phenyl moiety of the benzothiazoles to a LUMO of the benzene ring of the acceptors. The existence of this type of interaction is supported by HMO calculations on the donor molecules. On the other hand, the molecular complexes derived from acidic acceptors are stabilized, in addition to the π-π* interaction, by proton transfer from the hydroxyl or carboxylic group of the acceptor to the amino group of the aminothiazole donors. The ionization potentials of donors, electron affinities of acceptors as well as the energy of the CT complexes were computed from their u.v. and visible spectra.

In-situ intercalative oxidation of some pyridine derivatives within the cavity of the three-dimensional polymeric host [(Me3Pb)3Fe(CN)6]∞

Abstract Pyridine derivatives acting as guest species can be oxidized by the three-dimensional polymeric host [(Me 3 Pb) 3 Fe(CN) 6 ] ∞ forming yellow to brown or red colored CT complexes depending on the degree of charge transfer. The donor molecules can be intercalated within the cavity of the polymeric host in a 1/1 ratio after completion of the reaction. The CT complexes are weak semiconductors under the experimental conditions used.

Paramagnetic charge transfer complexes: new molecular composites via intercalation of thiazole and benzothiazole derivatives within the cavities of the 3D host polymers [(Me3E)3Fe(CN)6]∞; E - Sn or Pb

The three-dimensional (3D) polymers [Me3Sn)3Fe(CN)6]∞ (I) and [Me3pb)3Fe(CN)6]∞ (II) which have wide internal cavities capable of incapsulating voluminous organic compounds behave as host acceptors forming charge transfer complexes (CTC). Thiazole and benzothiazole derivatives acting as guest donor species are encapsulated within the cavities of the 3D polymeric hosts I or II forming yellow to green or red CTC having, in some cases, semiconducting properties. Some of the donors containing an amino group undergo polymerization within the cavities of the host polymers forming new molecular composites having pronounced electrical conductivity when doped in 2 M HCl solution. The interesting feature of these composites is the enhanced electronic conductivities exhibited by encapsulation of the conductive polymers within the cavities of the host 3D polymers.

Polyaniline and its derivatives intercalated in the channels of the 3D-[tris(trimethyl)tin hexacyanoferratel]∞

Abstract The polyaniline and its derivatives have been successfully intercalated within the channels of the 3D-[tris(trimethyl)tin hexacyanoferrate]∞ to yield novel semiconducting polymeric/CT intercalated complexes. The intercalated complexes are investigated by IR, UV and EPR spectra as well as elemental analysis. The electrical conductivity and the polymerization depend on the nature and number of substituents at the aniline ring as well as on the conditions of the reaction.

Unusual chromic behaviour of the solid supramolecular 3D polymers [(Me3Sn) nFe(CN)6]∞ (n = 34)

Abstract The orange polymer tris-(trimethyltin)hexacyanoferrate(III) ( 1 ) undergoes irreversible colour changes, turning pale green, green, pale blue and blue under the effect of UV irradiation at 366 nm, or pressure for 5 h, or heating at 100°C under nitrogen or in open air for 40 h, while the white polymer tetrakis-(trimethyltin)hexacyanoferrate(II) ( 2 ) turns grey and finally deep violet under the effect of pressure or heating (ca. 160°C) for a long time (ca. 60 h). The properties of the resulting coloured complexes were investigated by IR, UV-visible, ESR, Mossbauer spectroscopy, elemental and thermal analysis, and magnetic susceptibility measurements, indicating partial transformation of iron(III) to iron(II) in 1 and iron(II) to iron(III) in 2 respectively and suggesting the formation of stable semiconducting polymeric complexes of blue colour (final product), resembling that of Prussian blue, retaining their identity to form three-dimensional networks via trimethyltin connecting units.

The direct current electrical conductivity of the charge transfer complexes of some thiazoles and benzothiazoles with certain di- and trinitrobenzene derivatives

Abstract The DC electrical conductivity of 2-aminothiazole ( I ), 2-aminobenzothiazole ( II ), 2-amino-4-methylbenzothiazole ( III ) and 2-amino-6-nitrobenzothiazole ( IV ) and their charge transfer (CT) complexes with the acceptors, 1,3-dinitrobenzene ( 1 ), 3,4-dinitrobenzoic acid ( 2 ) and picric acid ( 3 ) were investigated. The positive temperature coefficients of the electrical conductivity of these thiazoles suggested their semiconducting characteristics. The CT complexes were classified into two main groups. The first group included the complexes I 1 , I 2 and IV 1,2,3 . All these complexes had negative temperature coefficients of resistance and revealed conventional semiconducting behaviour. Two different activation energies for the complexes I 2 , IV 2 and IV 3 indicated the presence of more than one conduction mechanism. The second group contained the complexes I 3 , II 1,2,3 . and III 1,2,3 . The thermal conductivity plots exhibited curves with two inflections and three regions. The slope of the line of a region and also its temperature range were found to depend upon the nature and structure of the complex. No correlation was found between the activation energies of the CT complexes and either the electron affinities of acceptors or the ionization potentials of donors. This was explained by assuming that the geometrical, and not the electronic, structure of the complexes was the determining factor.

Electrical and thermal behaviour of some Schiff bases and their charge transfer complexes with acidic acceptors

Abstract The electrical conductivities of some Schiff bases and their charge transfer complexes (CTCs) with 2,4-dinitrophenol and picric acid as acidic acceptors indicate that they behave as semiconductors within the investigated range of temperature. However, they are insulators at 300 K. DTA and IR spectra show the importance of the solvent of crystallization molecules in lowering the activation energy of the acceptors and the CTCs. The linear free energy relationship (LFER) indicates that the conduction process depends on the electronic structure.

Conductivity of polyaniline and its derivatives incorporated within the cavities of the three dimensional [tris(trimethyltin)hexacyano-ferrate]∞

Abstract The dependence of the electrical conductivity of aniline and its derivatives in situ intercalated within the cavities of the three dimensional polymeric host [(Me3Sn)3Fe(CN)6]∞, on temperature has been investigated. The conductivity values at 303 K, the activation energies and the energy gaps have been calculated. These novel polymeric intercalated complexes behave as good semiconductors. The conductivity depends on the structure of the aniline derivative and the conditions of the reaction.