A Caltech Library Service

Matrix Isolation and Characterization of 1,1-Diazenes


Sylwester, Alan Paul (1986) Matrix Isolation and Characterization of 1,1-Diazenes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/52cm-3b89.



The photochemical generation, matrix isolation and direct spectroscopic characterization of H2NN 3 is reported. UV (VIS filtered) photolysis of carbamoyl azide 15 in a rigid glass (2-MTHF, 80°K) generates blue-violet 3. The electronic absorption spectrum of 3 reveals a structured absorption curve λmax = 636 nm, λ0,0 = 695 nm for the n-π* transition of 3. This transition is blue shifted in a more polar glass (2-MTHF:nPrCN, 1:1, 80°K) to λmax = 624 nm, λ0,0 = 681 nm. The argon matrix FT-IR spectrum of 3 shows bands at 2865.55, 2807.20, 1863.20, 1574.16, and 1003.07 cm-1 (1:2000, Ar, 10°K). The characteristic N=N stretch for 3 at 1574.16 demonstrates the considerable double bond character in the 1,1-diazene. Incorporation of a terminal 15N label into H2N-15N 3-15N shifts the N=N stretch to 1547.64 cm-1. The argon matrix infrared spectra of 3, 3-15N, 3-d2, and 3-d2-15N are reported. Thermal decomposition of 3 (2-MTHF, 90°K) affords 2-tetrazene (λmax = 260 nm), trans HNNH 1 (λmax = 386 nm) and an unidentified species (λmax = 480 nm). Subsequent thermolysis (>100 K) affords NH3, N2H4, N+H4N-3, H2 and N2 products. Oirect irradiation of 3 in a glass (2-MTHF = 77°K) with visible light affords H2, N2, and trans-HNNH 1. Photodecomposition of matrix isolated 3 (Ar, 10°K) with visible light in the presence of CO affords formaldehyde (H2CO), trans-HNNH 1, H2, and N2. This represents the first direct observation of thermal and photochemical interconversion of H2N2 isomers.


Preliminary studies of the low temperature matrix isolation and spectroscopic characterization of 1,1-dimethyldiazene 7 and l, 1-di-isopropyldiazene 18 are reported. The UV (VIS filtered) photolysis of carbamoyl azides 13 and 17 in a rigid medium (organic glass, 80°K or Ar matrix, 10°K) provides a new general method for the photochemical generation of reactive 1,1-diazenes. This photochemical route is considered to proceed via the photo-Curtius rearrangement of a carbamoyl azide to an aminoisocyanate followed by photodecarbonylation to a 1,1-diazene and carbon monoxide. Electronic absorption spectroscopy (2-MTHF, 80°K) reveals structured absorption curves (n-π*) λmax = 556 nm, λ0,0 = 643 nm for 7 and λmax = 504 nm, λ0,0 = 620 nm for 18. 1,1-Dimethyldiazene 7 was independently generated by UV (VIS filtered) photolysis of (Z)-3,3-dimethyl-1-phenyltriazene-1-oxide 16 to afford 7 and nitrosobenzene. Matrix isolation FT-IR spectroscopy (Ar, 10°K) reveals the characteristic N=N stretch for 7 at 1600.96 cm-1. Incorporation of a terminal 15N label shifts this stretch to 1581.83 cm-1. The N:N stretch for 18 at 1600.92 cm-1 is 15N shifted to 1579.46 cm-1. Photochemical decomposition of 7 (Ar, 10°K) yields the infrared bands of ethane and an unidentified species (U) which is subsequently photolyzed to ethane. The effects of substitution on the electronic transitions and R2N=N stretches of 1,1-diazenes correlates with the trends of the isoelectronic carbonyl compounds. Thermolysis of 7 and 18 (2-MTHF, 90°K) yields red-orange 9 (λmax = 464 n, ε ≃ 3000 M-1 cm-1) and 30 (λmax = 474 nm, ε ≃ 3000 M-1 cm-1), respectively. These species are tentatively identified as the azomethinimine tautomers of the 1,1-diazenes with α-hydrogens. Irradiation of 7 and 18 at their n-π* transitions in the visible (2-MTHF, 80°K) also initially yields 9 and 30, respectively, in addition to the hydrocarbon products expected from nitrogen extrusion. Subsequent bimolecular decomposition of 9 (Ea = 8.2 ± 0.5 kcal/mol, log10 A = 1.8 ± 0.6) yields tetramethyl-2-tetrazene 19. Bimolecular decomposition of 9-d6 (Ea = 8.6 ± 0.5 kcal/mol, log10 A = 1.4 ± 0.6) reveals a deuterium isotope effect kH/kD = 6.7 at 190°K for loss of 9. Thermal decomposition of 30 affords hydrocarbon products 32, 33, and 34 expected for nitrogen extrusion from 1,1-diazene 18. The activation parameters for unimolecular decomposition of 30 are Ea = 16.8 ± 0.5 kcal/mol, log10 A = 11.8 ± 0.3.


The low-temperature 15N NMR spectrum of the 1,1-diazene, N-(2,2,6,6-tetramethylpiperidyl)nitrene (1) is reported. The 15N double- and mono-labeled 1,1-diazenes 1a and 1b were synthesized. The nitrene and amino nitrogens of 1 have resonances in dimethyl ether at -90°C at 917.0 and 321.4 ppm, respectively, downfield from anhydrous 15NH3, affording a chemical-shift difference of 595 ppm for the directly bonded nitrogen nuclei. The chemical shift of the ring nitrogen is consistent with an amino nitrogen whose lone pair is largely delocalized. The large downfield shift of the nitrene nitrogen is consistent with a large paramagnetic term due to a low-lying n-π* transition.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Dougherty, Dennis A.
Thesis Committee:
  • Dougherty, Dennis A. (chair)
  • Dervan, Peter B.
  • Grubbs, Robert H.
  • Marcus, Rudolph A.
Defense Date:22 July 1985
Funding AgencyGrant Number
W. R. Grace FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:10252019-122237282
Persistent URL:
Related URLs:
URLURL TypeDescription ItemArticle
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11863
Deposited By: Mel Ray
Deposited On:25 Oct 2019 22:47
Last Modified:16 Apr 2021 23:16

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page