Polymeric nitrogen

Poly-4-vinylpyridine is a versatile polymer since in the non-protonated form it may function as a polymeric nitrogen-donor ligand. Thus, redox centres may be anchored by coordination to pendant 4-pyridyl groups on the polymer chains. 

Fig. 9.5 Singly bonded polymeric nitrogen (cubic modification).

Fig. 14. Transmission spectra of polymeric nitrogen as a fimction of temperature. Spectra are shifted vertically for clarity. The characteristic peak of the T) phase is marked by a vertical arrow. Inset (a) shows the pressure dependence of the absorption spectra of nitrogen at very high pressures and room temperature. Gray lines represent the Tauc fits to the speetra in an appropriate spectral range. The determination of the energy gap from these measurements is obscured by additional losses caused by the presence of a fine ruby powder in the chamber. The high-energy absorption edge is most probably due to stress-induced absorption of diamond anvils (Ref. 62). (b) Urbach plots at 200 GPa and different temperatures (shifted vertically). Gray lines are guides to the eye.

Fig. 2.2. Raman spectra of polymeric nitrogen (cubic gauche structure) before and after heating at 110 GPa. The starting sample (300 K, bottom) is in the moiecuiar phase as indicated by the peak at 2400cmr . The bands at 1550-1300cm are due to the stressed diamond adjacent to the sample. Laser heating to 1990 K (top) transforms it to the poiymeric phase with a prominent peak at 840cm-U256J. 1GPa=1(fatm.

Metal Ion Binding at Polymeric Nitrogen Donor Ligands... 

The nitrogen atom has an electronegativity of 3.0. Thus for the nitrogen-nitrogen bond, the sum of the electronegativities is 6.0, whereas the difference AE is zero. Two nitrogen atoms therefore form a very stable multiple (triple) bond and polymeric nitrogen is not stable under normal conditions. 

Neutral molecules are the polynitrogen species of main interest because they represent pure polymerized nitrogen without the esthetic distraction of a counterion, because they have been the most difficult to realize experimentally, and because being pure nitrogen they are in principle the best candidates for high-energy-density materials. Closed-shell species would seem to be of particular interest, because most stable molecules fall into this class, but radicals and even-electron open-shell molecules will also be mentioned where appropriate. We will consider N3, N4, N5, Ne, N7, Ng, and larger molecules . 

Eremets MI, Gavriliuk AG, Trojan lA (2007) Single-crystalline polymeric nitrogen. Appl Phys Lett 90 171904... 

---