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Special Issue "Ferromagnetic Organic Radicals"

A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (1 September 2004).

Special Issue Editors

Dr. Antonio Alberola Catalan

Guest Editor
Dpto. de Quimica Fisica y Analitica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castellón, Spain
Special Issues and Collections in MDPI journals
Dr. Jeremy M. Rawson
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Guest Editor
Canada Research Chair in Molecular Materials, Dept of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
Interests: molecular magnetism; organic magnet; ferromagnet; antiferromagnet; ferrimagnet; density functional theory; exchange interaction
Special Issues and Collections in MDPI journals

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Editorial

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Open AccessEditorial
“Seek, and ye shall find” (Matthew 7:7)
Molecules 2004, 9(9), 713-715; https://doi.org/10.3390/90900713 - 31 Aug 2004
Cited by 1
Abstract
The preparation and characterisation of organic molecular magnets is a non-trivial task which touches on many contemporary issues within chemistry.[...] Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)

Research

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Open AccessArticle
Studies on TMPD:TCNB; a Donor-Acceptor with Room Temperature Paramagnetism and n-π Interaction†
Molecules 2004, 9(9), 808-814; https://doi.org/10.3390/90900808 - 31 Aug 2004
Cited by 6
Abstract
A donor-acceptor compound based on N,N,N′,N′-tetramethyl-p-phenylene-diamine and 1,2,4,5-tetracyanobenzene (TMPD:TCNB) has been synthesized. The crystalstructure of the black 1:1 complex formed between TMPD and TCNB has beendetermined by single crystal X-ray diffraction at room temperature. The compoundcrystallizes in the triclinic space group P-1 with [...] Read more.
A donor-acceptor compound based on N,N,N′,N′-tetramethyl-p-phenylene-diamine and 1,2,4,5-tetracyanobenzene (TMPD:TCNB) has been synthesized. The crystalstructure of the black 1:1 complex formed between TMPD and TCNB has beendetermined by single crystal X-ray diffraction at room temperature. The compoundcrystallizes in the triclinic space group P-1 with cell dimensions: a = 7.4986(15) å, b =7.6772(11) å, c = 8.0764(15) å, α = 78.822(12)°, β = 83.3779(19)°, γ = 86.289(17)°.TMPD and TCNB molecules are stacked alternately in infinite columns along the a-axis.The structure does not seem to show the usual π-π interaction between the two aromaticrings, but indicates an n-π interaction localized between the nitrogen atoms of the donorand the cyano groups of the acceptor. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
Theoretical Studies on Electronic States of Rh-C60. Possibility of a Room-temperature Organic Ferromagnet
Molecules 2004, 9(9), 792-807; https://doi.org/10.3390/90900792 - 31 Aug 2004
Cited by 9
Abstract
A possible mechanism for a ferromagnetic interaction in the rhombic (Rh) formof C60 (Rh-C60) is suggested on the basis of theoretical studies in relation to cage distortionof the C60 unit in the polymerized 2D-plane. Band structure calculations on Rh-C [...] Read more.
A possible mechanism for a ferromagnetic interaction in the rhombic (Rh) formof C60 (Rh-C60) is suggested on the basis of theoretical studies in relation to cage distortionof the C60 unit in the polymerized 2D-plane. Band structure calculations on Rh-C60 showthat cage distortion leads to competition between diamagnetic and ferromagnetic states,which give rise to the possibility of thermally populating the ferromagnetic state. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
Restricting Magnetic Interaction Pathways in Polyoxometalate Salts of Cationic Nitronyl Nitroxide Free Radicals
Molecules 2004, 9(9), 782-791; https://doi.org/10.3390/90900782 - 31 Aug 2004
Cited by 4
Abstract
Salts 1 and 2 that combine the [W6O19]2- Lindqvist anion with the cationicnitronyl nitroxide (NN) free radicals p-MepyNN+ and nBu3NCH2NN+ , respectively, havebeen synthesized and their structural and magnetic properties have been studied. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
Synthesis and Magnetic Properties of the Novel Dithiadiazolyl Radical, p-NCC6F4C6F4CNSSN
Molecules 2004, 9(9), 771-781; https://doi.org/10.3390/90900771 - 31 Aug 2004
Cited by 30
Abstract
The dithiadiazolyl radical p-NCC6F4C6F4CNSSN (4) retains its monomericnature in the solid state with molecules linked together into chains via supramolecularCN···S interactions. Variable temperature magnetic studies on 4 show that it behaves as anear-ideal Curie [...] Read more.
The dithiadiazolyl radical p-NCC6F4C6F4CNSSN (4) retains its monomericnature in the solid state with molecules linked together into chains via supramolecularCN···S interactions. Variable temperature magnetic studies on 4 show that it behaves as anear-ideal Curie paramagnet (|θ| less than 0.1 K), indicating negligible intermolecularexchange. The effective magnetic moment (1.78 μB) is temperature independent and inexcellent agreement with the value expected for an S = 1⁄2 paramagnet with g = 2.01(1.74μB). The lack of exchange coupling between radicals is attributed to the absence ofsignificant orbital overlap between radical centres. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
A First-Principles Analysis of the Magnetism of CuII Polynuclear Coordination Complexes: the Case of [Cu4(bpy)4(aspartate)2(H2O)3](ClO4)4•2.5H2O
Molecules 2004, 9(9), 757-770; https://doi.org/10.3390/90900757 - 31 Aug 2004
Cited by 11
Abstract
The magnetic structure of the [Cu4(bpy)4(aspartate)2(H2O)3](ClO4)4·2.5 H2Ocrystal — using fractional coordinates determined at room-temperature — has beenanalysed in detail. This analysis has been carried out by extending [...] Read more.
The magnetic structure of the [Cu4(bpy)4(aspartate)2(H2O)3](ClO4)4·2.5 H2Ocrystal — using fractional coordinates determined at room-temperature — has beenanalysed in detail. This analysis has been carried out by extending our first principlesbottom-up theoretical approach, which was initially designed to study through-spacemagnetic interactions, to handle through-bond magnetic interactions. The only input datarequired by this approach are the values of the computed JAB exchange parameters for allthe unique pairs of spin-containing centres. The results allow the magnetic structure ofthe crystal, which presents two types of isolated tetranuclear CuII clusters, to be definedin quantitative terms. Each of these clusters presents ferro and antiferromagneticinteractions, the former being stronger, although outnumbered by the latter. Thecomputed magnetic susceptibility curve shows the same qualitative features as theexperimental data. However, there are small differences that are presumed to beassociated with the use of room-temperature crystal coordinates. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
N-Salicylideneamine Derivatives with TEMPO Substituents
Molecules 2004, 9(9), 746-756; https://doi.org/10.3390/90900746 - 31 Aug 2004
Cited by 6
Abstract
Three N-salicylideneamine derivatives bearing TEMPO (2,2,6,6-tetra- methyl-1-piperidinyloxy) substituents were prepared in order to study their structure and property relationships and to investigate the possibilities of the existence of heat and/or light responsive magnetic properties. Curie-Weiss behavior with weak ferromagnetic intermolecular spin-spin interactions was [...] Read more.
Three N-salicylideneamine derivatives bearing TEMPO (2,2,6,6-tetra- methyl-1-piperidinyloxy) substituents were prepared in order to study their structure and property relationships and to investigate the possibilities of the existence of heat and/or light responsive magnetic properties. Curie-Weiss behavior with weak ferromagnetic intermolecular spin-spin interactions was observed in one of the radicals, while antiferromagnetic interactions were predominant for the other radicals and the structure-property relationships were investigated for the radical compounds from their crystal structures obtained by X-ray analyses. Preliminary results of the examination of their responses towards light and heat are also described. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
The Effects of Conjugation Path Variation on Electron Delocalization in Phenoxyl-Based Systems.
Molecules 2004, 9(9), 725-745; https://doi.org/10.3390/90900725 - 31 Aug 2004
Cited by 6
Abstract
A number of persistent 2,6-di-tert-butylphenoxyl based radicals were synthesized as models for unpaired spin delocalization as a function of conjugation pathway, and were investigated by ESR and UV-vis spectroscopy. Phenoxyl spin delocalizes significantly onto a para-phenyl ring, but further delocalization through a meta-vinyl [...] Read more.
A number of persistent 2,6-di-tert-butylphenoxyl based radicals were synthesized as models for unpaired spin delocalization as a function of conjugation pathway, and were investigated by ESR and UV-vis spectroscopy. Phenoxyl spin delocalizes significantly onto a para-phenyl ring, but further delocalization through a meta-vinyl or meta-carbonyl linkage is not detectable by ESR hyperfine coupling. UV- vis spectra do show a red shift of the longest wavelength transition for a carbonyl-type substituent by comparison to a vinyl substituent in the meta-position of a para-phenyl group. By comparison, a para-styryl substituent on the phenoxyl causes very large spin delocalization from the phenoxyl unit, with the largest hyperfine coupling being found on the ethenyl unit of the assemblage. This large delocalization accounts for the reactivity of radicals that incorporate such units. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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Open AccessArticle
New π-Delocalized Persistent Radicals
Molecules 2004, 9(9), 716-724; https://doi.org/10.3390/90900716 - 31 Aug 2004
Cited by 11
Abstract
Progress in the theoretical and experimental investigation of heterocyclic radicals suitable for incorporation into the structure of a liquid crystalline molecule is described. Five classes of heterocyclic systems are discussed, including their methods of preparation, stability and further functionalization to form potentially mesogenic [...] Read more.
Progress in the theoretical and experimental investigation of heterocyclic radicals suitable for incorporation into the structure of a liquid crystalline molecule is described. Five classes of heterocyclic systems are discussed, including their methods of preparation, stability and further functionalization to form potentially mesogenic materials. Full article
(This article belongs to the Special Issue Ferromagnetic Organic Radicals)
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