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Tetrathiafulvalene Hetero Radical Cation Dimerization in a Redox-Active [2]Catenane
Wang, Cheng,Dyar, Scott M.,Cao, Dennis,Fahrenbach, Albert C.,Horwitz, Noah,Colvin, Michael T.,Carmieli, Raanan,Stern, Charlotte L.,Dey, Sanjeev K.,Wasielewski, Michael R.,Stoddart, J. Fraser American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.46
<P>The electronic properties of tetrathiafulvalene (TTF) can be tuned by attaching electron-donating or electron-withdrawing substituents. An electron-rich macrocyclic polyether containing two TTF units of different constitutions, namely 4,4′-bis(hydroxymethyl)tetrathiafulvalene (OTTFO) and 4,4′-bisthiotetrathiafulvalene (STTFS), has been synthesized. On two-electron oxidation, a hetero radical dimer is formed between OTTFO<SUP>•+</SUP> and STTFS<SUP>•+</SUP>. The redox behavior of the macrocyclic polyether has been investigated by electrochemical techniques and UV–vis and electron paramagnetic resonance (EPR) spectroscopies. The [2]catenane in which the macrocyclic polyether is mechanically interlocked with the cyclobis(paraquat-<I>p</I>-phenylene) (CBPQT<SUP>4+</SUP>) ring has also been prepared using template-directed protocols. In the case of the [2]catenane, the formation of the TTF hetero radical dimer is prevented sterically by the CBPQT<SUP>4+</SUP> ring. After a one-electron oxidation, a 70:30 ratio of OTTFO<SUP>•+</SUP> to STTFS<SUP>•+</SUP> is present at equilibrium, and, as a result, two translational isomers of the [2]catenane associated with these electronically different isomeric states transpire. EPR titration spectroscopy and simulations reveal that the radical states of the two constitutionally different TTF units in the [2]catenane still experience long-range electronic intramolecular coupling interactions, despite the presence of the CBPQT<SUP>4+</SUP> ring, when one or both of them are oxidized to the radical cationic state. These findings in the case of both the free macrocyclic polyether and the [2]catenane have led to a deeper fundamental understanding of the mechanism of radical cation dimer formation between constitutionally different TTF units.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-46/ja307577t/production/images/medium/ja-2012-07577t_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja307577t'>ACS Electronic Supporting Info</A></P>
Oide, Shinichi,Liu, Jinyuan,Yun, Sung-Hwan,Wu, Dongliang,Michev, Alex,Choi, May Yee,Horwitz, Benjamin A.,Turgeon, B. Gillian American Society for Microbiology 2010 EUKARYOTIC CELL Vol.9 No.12
<B>ABSTRACT</B><P>Histidine kinase (HK) phosphorelay signaling is a major mechanism by which fungi sense their environment. The maize pathogen Cochliobolus heterostrophus has 21 HK genes, 4 candidate response regulator (RR) genes (<I>SSK1</I>, <I>SKN7</I>, <I>RIM15</I>, <I>REC1</I>), and 1 gene (<I>HPT1</I>) encoding a histidine phosphotransfer domain protein. Because most HKs are expected to signal through RRs, these were chosen for deletion. Except for pigment and slight growth alterations for <I>rim15</I> mutants, no measurable altered phenotypes were detected in <I>rim15</I> or <I>rec1</I> mutants. Ssk1p is required for virulence and affects fertility and proper timing of sexual development of heterothallic C. heterostrophus. Pseudothecia from crosses involving <I>ssk1</I> mutants ooze masses of single ascospores, and tetrads cannot be found. Wild-type pseudothecia do not ooze. Ssk1p represses asexual spore proliferation during the sexual phase, and lack of it dampens asexual spore proliferation during vegetative growth, compared to that of the wild type. <I>ssk1</I> mutants are heavily pigmented. Mutants lacking Skn7p do not display any of the above phenotypes; however, both <I>ssk1</I> and <I>skn7</I> mutants are hypersensitive to oxidative and osmotic stresses and <I>ssk1 skn7</I> mutants are more exaggerated in their spore-type balance phenotype and more sensitive to stress than single mutants. <I>ssk1</I> mutant phenotypes largely overlap <I>hog1</I> mutant phenotypes, and in both types of mutant, the Hog1 target gene, <I>MST1</I>, is not induced. <I>ssk1</I> and <I>hog1</I> mutants were examined in the homothallic cereal pathogen Gibberella zeae, and pathogenic and reproductive phases of development regulated by Ssk1 and Hog1 were found to mirror, but also vary from, those of C. heterostrophus.</P>