silicon and diazene

The effective use of photochromic systems based on azo compounds in a number of applications, especially biomedical and pharmacological ones, is impeded by the unresolved problem of their E⇆Z isomerization in the near-IR region, NIR (780-1400 nm). We have demonstrated at the TD-DFT, STEOM-DLPNO-CCSD and CASSCF-NEVPT2 levels of theory that the presence of a silylated diazene core -Si-N=N-Si- with three-, tetra- or five-coordinated silicon atoms practically guarantees the absorption of the E and Z forms of such derivatives in NIR and the amazing (185-400 nm) separation of their first absorption bands. In particular, the maximum λ

Topics: Azo Compounds; Imides; Silicon

The biological reduction of N(2) to give NH(3) may occur by one of two predominant pathways in which nitrogenous N(x)H(y) intermediates, including hydrazine (N(2)H(4)), diazene (N(2)H(2)), nitride (N(3-)) and imide (NH(2-)), may be involved. To test the validity of hypotheses on iron's direct role in the stepwise reduction of N(2), model systems for iron are needed. Such systems can test the chemical compatibility of iron with various proposed N(x)H(y) intermediates and the reactivity patterns of such species. Here we describe a trigonal bipyramidal Si(o-C(6)H(4)PR(2))(3)Fe-L scaffold (R = Ph or i-Pr) in which the apical site is occupied by nitrogenous ligands such as N(2), N(2)H(4), NH(3) and N(2)R. The system accommodates terminally bound N(2) in the three formal oxidation states (iron(0), +1 and +2). N(2) uptake is demonstrated by the displacement of its reduction partners NH(3) and N(2)H(4), and N(2) functionalizaton is illustrated by electrophilic silylation.

Topics: Ammonia; Coordination Complexes; Crystallography, X-Ray; Imides; Iron; Ligands; Molecular Conformation; Nitrogen; Oxidation-Reduction; Silicon