Photochemistry of Tetrasulfur Tetranitride: Laser Flash Photolysis and Quantum Chemical Study

Abstract

The photochemistry of tetrasulfur tetranitride (1) was studied in hexane solution by the laser flash photolysis technique (LFP). The experimental findings were interpreted using the results of previous matrix isolation studies (Pritchina, E.A.; Gritsan, N.P.; Bally, T.; Zibarev, A.V. Inorg. Chem. 2009, 48, 4075) and high-level quantum chemical calculations. LFP produces two primary intermediates, one of which is the boat-shaped 8-membered cyclic compound (2) and the other is the 6-membered S(3)N(3) cyclic compound carrying an exocyclic (S)-N═S group (3). The primary products 2 and 3 absorb a second photon and undergo transformation to the 6-membered S(3)N(3) cycle carrying an exocyclic (N)-S≡N group (4), which is very unstable and converts back to intermediate 3. The quantum yield of the primary product formation is close to unity even though the quantum yield of photodegradation of 1 is low (~0.01). Thus, 1 is a photochromic compound undergoing in solution the thermally reversible photochemical isomerization. The mechanism of the photochromic process was established, and the rate constants of the elementary reactions were measured.

Analysis of the Explosive Properties of Tetrasulfur Tetranitride, S4N4

“…Photochemical excitation (λ=254 and 365 nm) of S 4 N 4 in Ar matrix at 10 K has revealed the transient formation of a boat type ( C s ) conformer of S 4 N 4 [51,52] calculated to be ∼30 kJ higher in energy (in hexane solvent) than D 2d similar to the one reported in ref. [43].…”

Neutral binary chalcogen–nitrogen and ternary S,N,P molecules: new structures, bonding insights and potential applications

“…50 It is also noted that the related derivative S 3 N 3 -NvS has been identified as a short-lived intermediate generated upon flash photolyis of S 4 N 4 . 51…”

The Nature of Transannular Interactions in E4N4 and E82+ (E = S, Se)

“…The electronic structures of 1 – 4 have received renewed attention. For example, the strength of the S···S interaction in S 4 N 4 was recently estimated to be on the order of typical hydrogen bonds, and the electrochemical and photochemical behaviors of S 4 N 4 have been the subject of several detailed and complementary investigations. − Furthermore, bonding in dithiatetrazocines has been discussed in the context of homoaromaticity , and the importance of these analyses highlighted in a Nature Chemistry commentary . Consequently, it is of importance that an unambiguous answer to the question of the physical origin of transannular interactions in 1 – 4 is found.…”