Document Detail


Dicopper(II) Metallacyclophanes with Electroswitchable Polymethyl-Substituted para-Phenylene Spacers.
MedLine Citation:
PMID:  23873803     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Double-stranded anionic dinuclear copper(II) metallacyclic complexes of the paracyclophane type [Cu2 L2 ](4-) have been prepared by the Cu(II) -mediated self-assembly of different para-phenylenebis(oxamato) bridging ligands with either zero-, one-, or four-electron-donating methyl substituents (L=N,N'-para-phenylenebis(oxamate) (ppba; 1), 2-methyl- N,N'-para-phenylenebis(oxamate) (Meppba; 2), and 2,3,5,6-tetramethyl- N,N'-para-phenylenebis(oxamate) (Me4 ppba; 3)). These complexes have been isolated as their tetra-n-butylammonium (1 a-3 a), lithium(I) (1 b-3 b), and tetraphenylphosphonium salts (1 c-3 c). The X-ray crystal structures of 1 a and 3 c show a parallel-displaced π-stacked conformation with a smaller deviation from perpendicularity between the two benzene rings and the basal planes of the square planar Cu(II) ions when increasing the number of methyl substituents (average dihedral angles (ϕ) of 58.72(7) and 73.67(5)° for 1 a and 3 c, respectively). Variable-temperature (2.0-300 K) magnetic-susceptibility measurements show an overall increase of the intramolecular antiferromagnetic coupling with the number of methyl substituents onto the para-phenylene spacers (-J=75-95, 100-124, and 128-144 cm(-1) for 1 a-c, 2 a-c, and 3 a-c, respectively; H=-JS1 ×S2 ). Cyclic voltammetry (CV) measurements show a reversible one-electron oxidation of the double polymethyl-substituted para-phenylenediamidate bridging skeleton at a relatively low formal potential that decreases with the number of methyl substituents (E1 =+0.33, +0.24, and +0.15 V vs. SCE for 1-3, respectively). The monooxidized dicopper(II) π-radical cation species 3' prepared by the chemical oxidation of 3 with bromine exhibits intense metal-to-ligand charge-transfer (MLCT) transitions in the visible and near-IR (λmax =595 and 875 nm, respectively) regions together with a rhombic EPR signal with a seven-line splitting pattern due to hyperfine coupling with the nuclear spin of the two Cu(II) ions. Density functional (DF) calculations for 3' evidence a characteristic iminoquinonoid-type short-long-short alternating sequence of CN and CC bonds for both tetramethyl-para-phenylenediamidate bridges and a large amount of spin density of negative sign mainly delocalized along each of the four benzene C atoms directly attached to the amidate N atoms, which is in agreement with a fully delocalized π-stacked monoradical ligand description. Hence, the spins of the two Cu(II) ions (SCu =1/2) that are antiparallel aligned in 3 (OFF state) become parallel in 3' (ON state). Further developments may be then envisaged for this new permethylated dicopper(II) paracyclophane with a redox noninnocent ligand as a prototype for molecular magnetic electroswitch.
Authors:
Jesús Ferrando-Soria; María Castellano; Rafael Ruiz-García; Joan Cano; Miguel Julve; Francesc Lloret; Catalina Ruiz-Pérez; Jorge Pasán; Laura Cañadillas-Delgado; Donatella Armentano; Yves Journaux; Emilio Pardo
Related Documents :
23005913 - Photophysical properties of 7-(diethylamino) coumarin-3-carboxylic acid in the nanocage...
17107783 - Feasibility of hydrogen production in thermophilic mixed fermentation by natural anaero...
24014893 - Cyanovanadate(iii) complexes as novel additives for efficient generation of volatile ca...
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-7-22
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  -     ISSN:  1521-3765     ISO Abbreviation:  Chemistry     Publication Date:  2013 Jul 
Date Detail:
Created Date:  2013-7-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Affiliation:
Instituto de Ciencia Molecular (ICMol), Universitat de València, 46980 Paterna, Valencia (Spain), Fax: (+34) 963544322.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Activation of angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis attenuates the cardiac reac...
Next Document:  The changing incidence of primary central nervous system lymphoma is driven primarily by the changin...