Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds::the role of iodine Lewis basicity

The title molecules are sought in connection with various synthetic applications. The aliphatic fluorous alcohols RfnCH2OH (Rfn = CF3(CF2)n–1; n = 11, 13, 15) are converted to the triflates RfnCH2OTf (Tf2O, pyridine; 22–61%) and then to RfnCH2I (NaI, acetone; 58–69%). Subsequent reactions with NaOCl/HCl give iodine(III) dichlorides RfnCH2ICl2 (n = 11, 13; 33–81%), which slowly evolve Cl2. The ethereal fluorous alcohols CF3CF2CF2O(CF(CF3)CF2O)xCF(CF3)CH2OH (x = 2–5) are similarly converted to triflates and then to iodides, but efforts to generate the corresponding dichlorides fail. Substrates lacking a methylene group, RfnI, are also inert, but additions of TMSCl to bis(trifluoroacetates) RfnI(OCOCF3)2 appear to generate RfnICl2, which rapidly evolve Cl2. The aromatic fluorous iodides 1,3-Rf6C6H4I, 1,4-Rf6C6H4I, and 1,3-Rf10C6H4I are prepared from the corresponding diiodides, copper, and RfnI (110–130 °C, 50–60%), and afford quite stable RfnC6H4ICl2 species upon reaction with NaOCl/HCl (80–89%). Iodinations of 1,3-(Rf6)2C6H4 and 1,3-(Rf8CH2CH2)2C6H4 (NIS or I2/H5IO6) give 1,3,5-(Rf6)2C6H3I and 1,2,4-(Rf8CH2CH2)2C6H3I (77–93%). The former, the crystal structure of which is determined, reacts with Cl2 to give a 75:25 ArICl2/ArI mixture, but partial Cl2 evolution occurs upon work-up. The latter gives the easily isolated dichloride 1,2,4-(Rf8CH2CH2)2C6H3ICl2 (89%). The relative thermodynamic ease of dichlorination of these and other iodine(I) compounds is probed by DFT calculations

Circadian pacemaker coupling by multi-peptidergic neurons in the cockroach Leucophaea maderae

Lesion and transplantation studies in the cockroach, Leucophaea maderae, have located its bilaterally symmetric circadian pacemakers necessary for driving circadian locomotor activity rhythms to the accessory medulla of the optic lobes. The accessory medulla comprises a network of peptidergic neurons, including pigment-dispersing factor (PDF)-expressing presumptive circadian pacemaker cells. At least three of the PDF-expressing neurons directly connect the two accessory medullae, apparently as a circadian coupling pathway. Here, the PDF-expressing circadian coupling pathways were examined for peptide colocalization by tracer experiments and double-label immunohistochemistry with antisera against PDF, FMRFamide, and Asn13-orcokinin. A fourth group of contralaterally projecting medulla neurons was identified, additional to the three known groups. Group one of the contralaterally projecting medulla neurons contained up to four PDF-expressing cells. Of these, three medium-sized PDF-immunoreactive neurons coexpressed FMRFamide and Asn13-orcokinin immunoreactivity. However, the contralaterally projecting largest PDF neuron showed no further peptide colocalization, as was also the case for the other large PDF-expressing medulla cells, allowing the easy identification of this cell group. Although two-thirds of all PDF-expressing medulla neurons coexpressed FMRFamide and orcokinin immunoreactivity in their somata, colocalization of PDF and FMRFamide immunoreactivity was observed in only a few termination sites. Colocalization of PDF and orcokinin immunoreactivity was never observed in any of the terminals or optic commissures. We suggest that circadian pacemaker cells employ axonal peptide sorting to phase-control physiological processes at specific times of the day

Biological Earth observation with animal sensors.

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Biological Earth observation with animal sensors

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Theoretical Aspects of Werner Complexes and Molecular Devices

This dissertation begins with the first comprehensive review of molecular gyroscopes. The following two chapters feature combined experimental/computational studies. In the first, equilibria involving gyroscope-like complexes and geometric isomers are measured and the data interpreted with molecular dynamics simulations and DFT calculations. In the second, trigonal bipyramidal diiron tetraphosphorus complexes that have parallel P–Fe–P axes and the potential for coupled Fe(CO)3 rotators are examined. Here the DFT studies focus mainly on electronic structure and IR properties. The rotators can be removed from the gyroscope-like complexes to give unprecedented dibridgehead diphosphines with long (CH2)n linkers. Their conformational, dynamic, and NMR properties are interrogated by simulated annealing and DFT calculations, helping to rationalize observed behavior and predicting properties of molecules that remain to be synthesized. Another major class of molecules investigated is polyynes H(C≡C)n'H which are of special interest at long chain lengths (models for the polymeric sp carbon allotrope carbyne). Nucleus independent chemical shifts are revealing an absence of special shielding regions and DFT calculations provide highly accurate chemical shift values, including polyynes with platinum endgroups. Complexes with four platinum corners and four –(C≡C)2– edges can be accessed. Electrostatic potential maps show highly negatively charged cores that explain the strong affinities of these species for ammonium salts. DFT calculations also establish very similar energies for planar vs. puckered conformations, both of which have been observed crystallographically: electronic structures and equilibria involving Pt3 and Pt5 homologs are also thoroughly explored. Werner complexes of the type [Co(en)3]3+ 3X– (en = 1,2-ethylenediamine) have also been extensively investigated. In one study, the intricate stereochemical and conformation properties are reviewed including substituted derivatives using conventions from both organic and inorganic chemistry. In another, >150 crystal structures of [Co(en)3]3+ salts have been analyzed with respect to hydrogen bonding between the NH groups and the counteranions. Diverse motifs could be identified and a nomenclature syntax developed