title: Molecular diodes and ultra-thin organic rectifying junctions: Au-S-CnH2n-Q3CNQ and TCNQ derivatives.
abstract: Attempts to obtain derivatives of the molecular diode, 2-{4-[1-cyano-2-(1-(omega-acetylsulfanylalkyl)-1H-quinolin-4-ylidene)-ethylidene]-cyclohexa-2,5-dienylidene}-malonitrile [1, CH(3)CO-S-C(n)H(2n)-Q3CNQ], from either 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (TCNQF(4)) or 2,3,5,6-tetramethyl-7,7,8,8-tetracyano-p-quinodimethane (TMTCNQ) result in ring closure via the cyano group of the pi-bridge and yield di-substituted analogues: 2-{2,3,5,6-tetrafluoro-4-[6-(10-acetylsulfanyldecyl)-3-(1-(10-acetylsulfanyldecyl)-1H-quinolin-4-ylidenemethyl)-6H-benzo[f][1,7]naphthyridin-2-ylidene]-cyclohexa-2,5-dienylidene}-malonitrile (2a) and the 2,3,5,6-tetramethyl derivative (2b). Self-assembled monolayers (SAMs) of these donor-(pi-bridge)-acceptor molecular diodes exhibit asymmetric current-voltage characteristics with electron flow at forward bias from the top contact to surface C(CN)(2) groups. Comparison is made with I-V curves from ultra-thin films of an organic rectifying junction in which TCNQ(-) is electron-donating and a donor-(sigma-bridge)-acceptor diode in which TCNQ degrees is electron-accepting.
authors.affiliation: The Nanomaterials Group, School of Chemistry, University of Wales, Bangor, Gwynedd, UK. g.j.ashwell@bangor.ac.uk
authors.forename: Geoffrey J
authors.initials: GJ
authors.lastname: Ashwell
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Moczko
authors.forename: Marta
authors.initials: M
authors.lastname: Sujka
authors.forename: Anna
authors.initials: A
authors.lastname: Chwialkowska
authors.forename: L R
authors.initials: LR
authors.lastname: Hermann High
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sandman
mesh_terms: D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012666:Semiconductors; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry*; D013997:Time Factors
chemical_list: D009570:Nitriles; D009942:Organometallic Compounds; D011108:Polymers; C013703:tetracyanoquinodimethane; D013455:Sulfur; D006046:Gold; C000945:dicyanmethane; D004121:Dimethyl Sulfoxide