Schreiner, Peter R.Wegner, Hermann A.Qian, WeiyuWeiyuQian2025-09-042025-09-042025https://jlupub.ub.uni-giessen.de/handle/jlupub/20798https://doi.org/10.22029/jlupub-20149The stability and instability is one of the most fundamental dualities in chemistry, which governs the essence of reactivity with a linkage of energy through kinetic and thermodynamic principles, as well as quantum-mechanical tunneling. The "unstable" species, driven by a natural inclination, strives to transform into a "stable" state, minimizing energy and pushing the reaction equilibrium. Conversely, a "stable" species must be "compelled" into an unstable state—whether by external forces or chemical manipulation—to unlock its reactivity or achieve energy storage. This dynamic relationship underscores the intrinsic interdependence of stability and instability; they are not absolutes but rather exist in a state of constant tension, capable of mutual inversion depending on context and conditions. From a philosophical perspective, stability and instability can be viewed as two sides of the same coin (like Apollonian and Dionysian, from Die Geburt der Tragödie aus dem Geiste der Musik, Friedrich Nietzsche), where each defines and elevates the significance of the other. Stability gives instability its allure of transient, prompting the quest to capture fleeting species that defy conventional norms. Meanwhile, instability imbues stability with its intrinsic value, as the effort to stabilize the ephemeral drives innovation in chemistry. This duality reflects a broader natural order, where opposites not only coexist but also fuel progress, challenge boundaries, and inspire creativity. In this thesis, I’m going to constitute unstable "oligomer" (higher neutral nitrogen allotropes) with the units of stable dinitrogen, explore methods to generate and study the chemistry of unstable heavier analogs of stable dinitrogen, and investigate novel properties of highly reactive, electron-deficient species that violate the octet rule in main group elements. This endeavor embodies a philosophical and scientific journey—transforming the transient into the tangible, the unstable into the cherished, and the elusive into the achievable. In the first publication, the interstellar candidate phosphorus mononitride PN, a metastable species under ambient conditions, was generated through high-vacuum flash pyrolysis of (o-phenyldioxyl)phosphinoazide in cryogenic matrices. Moreover, an elusive o-benzoquinone-PN complex formed and its recombination to (o-phenyldioxyl)-λ5-phosphinonitrile was observed upon irradiation with the light λ = 523 nm, which demonstrates for the first time the reactivity of PN towards an organic molecule. In the second publication, we report the in situ characterization of triplet phenylarsinidene by matrix-isolation infrared and UV/Vis spectroscopy. Doping the matrices containing phenylarsinidene with molecular oxygen leads to the formation of hitherto unknown kinetic intermediate anti-dioxyphenylarsine, which demonstrates a completely different reactivity with corresponding phenylnitrene and phenylphosphinidene. The anti-dioxyphenylarsine undergoes isomerization to novel dioxophenylarsine upon 465 nm irradiation. In the third publication, we report the synthesis and spectroscopic characterization of vinylarsinidene, a higher congener of vinylnitrene. Triplet vinylarsinidene was characterized by IR and UV/Vis spectroscopy and displays remarkably rich unimolecular photochemistry. Upon selective photoirradiation, it rearranges to vinylidenearsine, 2H-arsirene, or an arsinidene (H–As) acetylene complex. Furthermore, the stability of vinylphosphinidene was projected with multireference computations. In the fourth publication, the first example of scalably synthesizable neutral nitrogen allotrope, C2h-N6 was prepared in the gas-phase at ambient temperature, followed by characterized in argon matrices at 10 K or neatly as a film at liquid nitrogen temperature (77 K), demonstrating unexpectedly high stability. Energetic performance computations at the CCSD(T)/cc-pVTZ level with Kamlet-Jacob equation predict an excellent detonation performance over several well-known explosives, for example, TNT (2,4,6-trinitrotoluene) and RDX (1,3,5-trinitro-1,3,5-triazinane).enIn Copyrightddc:540