Structural characterization of straight-chain trioxides and their metal and organometallic complexes

Siljanovska Virant, Ana (avtor), Cerkovnik, Janez (mentor)

The aim of this thesis was to gain insight into the structure of the elusive trioxidane molecule (H$_2$O$_3$) and its derivatives by different methods of stabilization and subsequent structural characterization by single-crystal X-ray diffraction. First, an optimized preparation of pure H$_2$O$_3$ solutions is presented and the use of molecular sieves as desiccants was investigated. It was shown that although these sieves effectively reduce the water content, they also contribute to the gradual degradation of H$_2$O$_3$. To gain structural insights into H$_2$O$_3$ in the solid state, various crystallization approaches were evaluated. Salts of weakly coordinating anions (WCAs) were tested for complex formation with trioxidane. Insight into the structure and stability of the hypothesized complexes was also gained through a preliminary DFT study. In an effort to capture H$_2$O$_3$ by hydrogen bonding, organopnictogen(V) oxides were investigated as potential hydrogen-bond acceptors. A novel and efficient synthetic route for Ph$_3$AsO was developed, which led to a systematic crystallographic study of hydrogen-bonded cocrystals with this compound. Several new cocrystals of Ph$_3$AsO with H$_2$O$_2$ and gem-dihydroperoxides were obtained and structurally characterized. Hydrogen peroxide was shown to form a chair-like cocrystal arrangement, [Ph$_3$AsO·H$_2$O$_2$]$_2$·H$_2$O$_2$, stabilized by moderate hydrogen bonding, which increases its stability and allows potential use in organic oxidation reactions. This is the first systematic study of hydrogen-bonded cocrystals with Ph$_3$AsO, expanding the understanding of its chemistry and demonstrating its potential for crystal engineering. The success of Ph$_3$AsO as a hydrogen-bond acceptor and coformer with H$_2$O$_2$ and gem‑dihydroperoxides prompted us to investigate its hydrogen-bonding propensity towards H$_2$O$_3$. The formation of hydrogen bonds enabled the crystallization of Ph$_3$AsO cocrystals with H$_2$O$_3$. This is the first structure of anti-H$_2$O$_3$ in the solid-state bonded to two Ph$_3$AsO·H$_2$O moieties. In addition, the stability of the adduct in solution was monitored by low-temperature NMR spectroscopy. The range of hydrogen-bond acceptors was extended to phosphine oxides, with Ph$_3$PO and Me$_3$PO leading to single crystals. In the cocrystal with Ph$_3$PO, trioxidane is present in its syn form. This is the first structural information about the less stable conformer of H$_2$O$_3$. The bulkiness of the phenyl rings provides prolonged stability, so that a Raman spectrum of the crystal could be recorded at room temperature. However, the trioxidane molecule in both cocrystals was found to be disordered. Me3PO proved to be the most suitable hydrogen-bond acceptor for cocrystal formation, as trioxidane in this structure is well embedded as anti-H$_2$O$_3$ between the small Me$_3$PO molecules and the geometric parameters could be defined in detail. In addition, an optimized synthetic route for the sterically shielding NHC ligand IPr** is reported. This ligand was used to synthesize a series of copper and silver complexes, including an air‑sensitive hydrido complex capable of O$_3$ insertion. Finally, the results of this work are of fundamental importance for the structural elucidation of short-lived, unstable, exotic molecules. In addition, low‑temperature isolation and characterization techniques, which are relevant to a variety of scientific fields, were developed and perfected.

• Jezik: Angleški jezik
• Ključne besede: trioxidane, crystal structure, cocrystals, hydrogen bonds, peroxides, NHC
• Vrsta gradiva: Doktorsko delo/naloga
• Tipologija: 2.08 - Doktorska disertacija
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Leto izida: 2026
• PID: 20.500.12556/RUL-179253
• COBISS.SI-ID: 271620099
• Datum objave v RUL: 09.02.2026

Sekundarni jezik

• Jezik: Slovenski jezik
• Naslov: Strukturna karakterizacija verižnih trioksidov in njihovih kovinskih in organokovinskih kompleksov

Izvleček

Cilj te doktorske disertacije je raziskati strukturo izmuzljive molekule trioksidana (H$_2$O$_3$) in njegovih derivatov z različnimi metodami stabilizacije in sledečo strukturno karakterizacijo z rentgensko difrakcijo na monokristalih. Najprej je predstavljena optimizirana priprava čistih raztopin H$_2$O$_3$, pri čemer smo proučili tudi uporabo molekulskih sit kot sušilnih sredstev. Izkazalo se je, da molekulska sita sicer učinkovito zmanjšajo vsebnost vode, vendar hkrati povzročijo tudi postopen razpad molekul H$_2$O$_3$. Za določitev strukture H$_2$O$_3$ v trdnem stanju smo testirali različne načine kristalizacije. Proučevali smo tvorbo kompleksov med solmi šibko koordinirajočih anionov (WCA) in trioksidanom. Strukturo in stabilnost koordinacije smo proučili tudi s preliminarnimi DFT študijami. Za ujetje H$_2$O$_3$ prek vodikovih vezi so bili kot potencialni akceptorji vodikovih vezi proučeni oksidi organopniktogenov(V). Razvili smo novo in učinkovito sintezno pot do Ph$_3$AsO, kar je omogočilo sistematično kristalografsko študijo vodikovih vezi v kokristalih s to spojino. Pridobljenih in strukturno opisanih je bilo več novih kokristalov Ph$_3$AsO s H$_2$O$_2$ in gem dihidroperoksidi. Pokazali smo, da vodikov peroksid tvori strukturo v obliki stola [Ph$_3$AsO·H$_2$O$_2$]2·H$_2$O$_2$, stabilizirano z zmerno močnimi vodikovimi vezmi, kar povečuje njegovo stabilnost in omogoča potencialno uporabo pri reakcijah oksidacije. To je prva sistematična študija kokristalov z vodikovimi vezmi pri Ph$_3$AsO, ki prispeva k razumevanju njegove kemije in dokazuje njegov potencial za uporabo v kristalnem inženirstvu. Uspeh Ph$_3$AsO kot akceptorja vodikovih vezi s H$_2$O$_2$ in organskih dihidroperoksidov nas je spodbudil k raziskavi njegove sposobnosti tvorbe vodikovih vezi s H$_2$O$_3$. Tvorba vodikovih vezi je omogočila nastanek in izolacijo kokristalov Ph$_3$AsO s H$_2$O$_3$. To je prva kristalna struktura anti H$_2$O$_3$, kjer je H2O3 vezan na dve enoti Ph$_3$AsO·H$_2$O. Poleg tega smo spremljali stabilnost adukta v raztopini z NMR spektroskopijo pri nizkih temperaturah. Nabor akceptorjev vodikovih vezi smo razširili na fosfin okside, pri čemer sta Ph$_3$PO in Me$_3$PO omogočila tvorbo monokristalov. V kokristalu s Ph$_3$PO je trioksidan prisoten v syn-obliki. To je prva strukturna informacija o manj stabilnem syn-H$_2$O$_3$ konformeru. Sterična oviranost fenilnih skupin prispeva k podaljšanju stabilnosti, kar je omogočilo snemanje ramanskega spektra pri sobni temperaturi. Me$_3$PO se je izkazal za najbolj ustreznega akceptorja vodikovih vezi za tvorbo kokristalov, saj je trioksidan v tem kokristalu v anti-konformaciji dobro vpet med majhnimi molekulami Me$_3$PO, kar je omogočilo natančno določitev njegovih geometrijskih parametrov. Poleg tega smo razvili optimizirano sintezno pot za sterično oviran NHC ligand IPr**. Ta ligand je bil uporabljen za sintezo serije bakrovih in srebrovih kompleksov, vključno z na zrak občutljivim hidridnim kompleksom, sposobnim vstavitve O$_3$. Nenazadnje so rezultati tega dela bistvenega pomena za določitev struktur kratkoživih, nestabilnih in eksotičnih molekul. Poleg tega smo razvili in izpopolnili tehnike izolacije in karakterizacije pri nizkih temperaturah, ki so pomembne za različna znanstvena področja.

• Ključne besede: trioksidan, kristalna struktura, kokristali, vodikove vezi, peroksidi, NHC