The coordination number–photophysical properties relationship of trianthrylphosphorus compounds: doubly locked fluorescence of anthryl groups

The First Example of the Friedel-Crafts Cyclization Leading to (10-Hydroxy-9,10-dihydroanthr-9-yl)phosphonium Salts without the Expected Bradsher Dehydration

The reaction of (ortho-acetalaryl)arylmethanols with various phosphines PR1R2R3 (R1 = R2 = R3 = Ph; R1 = R2 = Ph, R3 = Me and R1 = R2 = Me, R3 = Ph) under acidic conditions (e.g., HCl, HBF4, TsOH) unexpectedly led to the formation of (10-hydroxy-9,10-dihydroanthr-9-yl)phosphonium salts instead of the corresponding anthryl phosphonium salts. The cyclization occurred according to the Friedel-Crafts mechanism but without the usually observed Bradsher dehydration, giving cyclic products in the form of cis/trans isomers and their conformers. In case of electron-rich and less-hindered dimethylphenylphosphine, all four stereoisomers were recorded in 31P{1H} NMR spectra, while for the other phosphines, only the two most stable cis/trans stereoisomers were detected. This study was supported by DFT and NCI calculations in combination with FT-IR analysis.

Three-Component Synthesis of Dioxaphosphorane-Fused Diphosphacycles Exhibiting Unique Dynamic Fluorescence "On/Off" Properties

Rigidly planar polycyclic phosphacycles featuring an internal dioxaphosphorane are promising photofunctional materials. However, the lack of efficient synthetic methods resulted in limited structural diversities which significantly hampered extensive study. Herein, we report a straightforward three-component synthesis of novel dioxaphosphorane-fused diphosphacycles with distinctive photophysical properties. Control experiments and theory calculations were performed to account for a plausible reaction mechanism. We also systematically investigated the structure-property relationships of these unprecedented platforms by combining experiments (X-ray analysis, optical and redox properties) and theoretical computations. Based on their unique structure and properties, a novel fluorescent switch for pH sensing was revealed by a dynamic ring-opening/ring-closing process.

Comprehensive Review on Synthesis, Properties, and Applications of Phosphorus (PIII, PIV, PV) Substituted Acenes with More Than Two Fused Benzene Rings

This comprehensive review, covering the years 1968-2022, is not only a retrospective investigation of a certain group of linearly fused aromatics, called acenes, but also a presentation of the current state of the knowledge on the synthesis, reactions, and applications of these compounds. Their characteristic feature is substitution of the aromatic system by one, two, or three organophosphorus groups, which determine their properties and applications. The (P^III, P^IV, P^V) phosphorus atom in organophosphorus groups is linked to the acene directly by a P-C_sp2 bond or indirectly through an oxygen atom by a P-O-C_sp2 bond.

Design, Synthesis, and Temperature-Driven Molecular Conformation-Dependent Delayed Fluorescence Characteristics of Dianthrylboron-Based Donor-Acceptor Systems

We report a simple and novel molecular design strategy to enhance rISC in boron-based donor-acceptor systems to achieve improved delayed fluorescence characteristics. Dianthrylboryl ((An)₂B)-based aryl aminoboranes 1 (donor: phenothiazine) and 2 (donor: N,N-diphenylamine) were synthesized by a simple one-pot procedure. The energy of the electronic excited states in 1 and 2 were modulated by varying the arylamine donor strength and electronic coupling between D and A moieties. The presence of a large π-system (anthryl moiety) on boron enhances the electronic communication between donor arylamine and acceptor boryl moieties, and hence, both 1 and 2 exhibit delayed fluorescence characteristics in a broad range of temperatures (80-300 K). Single crystal X-ray analysis and temperature-dependent photophysical studies together with theoretical studies were carried out to rationalize the observed intriguing optical signatures of 1 and 2.

Synthesis and characterisation of fluorescent aminophosphines and their coordination to gold(i)

Three novel fluorescent aminophosphine ligands have been synthesised that incorporate napthyl (L1), pyrenyl (L2) and anthraquinone (L3) chromophores into their structures. The ligands react with [AuCl(tht)] (tht = tetrahydrothiophene) to give neutral complexes of the form [AuCl(L1-3)]. Solid state, X-ray crystallographic data was obtained for the anthraquinone derivative, [AuCl(L3)], and showed a distorted linear coordination geometry at Au(i). The packing structure also revealed a number of intermolecular π-π interactions that involve the anthraquinone and phenyl units of the aminophosphine ligand. 31P NMR spectroscopic data revealed δP values of +42.2 (L1), +42.1 (L2) and +26.1 (L3) ppm, which shifted downfield upon coordination to Au(i) to +64.6, +64.7, and +55.8 ppm, respectively. Supporting TD-DFT studies were able to reproduce the structure and 31P NMR chemical shifts of [AuCl(L3)] as well as rationalise the HOMO-LUMO compositions. Photophysical studies showed that the appended fluorophore dominates the absorption and emission properties for the ligands and complexes, with the anthraquinone derivatives showing visible emission at ca. 570 nm which was attributed to the intramolecular charge transfer character of the phosphinoaminoanthraquinone fragment.

Molecular architectures of multi-anthracene assemblies

Anthracene, with its molecular panel-like shape and robust photophysical behaviour, is a versatile building block that is widely used to construct attractive and functional molecules and molecular assemblies through covalent and non-covalent linkages. The intrinsic photophysical, photochemical and chemical properties of the embedded anthracenes often interact to engender desirable chemical behaviours and properties in multi-anthracene assemblies. This review article focuses on molecular architectures with linear, cyclic, cage, and capsule shapes, each containing three or more anthracene subunits.

Phosphoryl group as a strong σ-donor anionic phosphine-type ligand: a combined experimental and theoretical study on long-lived room temperature luminescence of the [Ru(tpy)(bpy)(Ph2PO)]+ complex

A phosphoryl Ru(II) polypyridyl complex was prepared in a one-pot process. Theoretical analysis suggests that the phosphoryl ligand may be viewed as a strong σ-donor anionic phosphine L-type ligand. State-of-the-art free-energy profile calculations on the excited states demonstrate that both favorable thermodynamic and kinetic factors are responsible for the remarkable room temperature luminescence properties of the phosphoryl complex.

Phosphorus as a carbon copy and as a photocopy: New conjugated materials featuring multiply bonded phosphorus

Phosphaalkenes (RP=CR2) and diphosphenes (RP=PR) are main group analogues of alkenes (R2C=CR2). Molecules featuring such multiply bonded phosphorus functionalities often display structural features and chemical reactivities that mimic their purely organic counterparts, lending credence to the claim that these compounds are “carbon copies”. We have been expanding this analogy to include oligomers and polymers with extended conjugation that directly involve P=C and P=P units. Many of these materials, however, display little or no photoluminescence (PL). This article summarizes our efforts to understand P=C and P=P photobehavior and to produce materials having significant PL that mimic or “photocopy” the PL properties of the phosphorus-free systems. Recent materials based on benzoxaphospholes (BOPs), benzobisoxaphospholes (BBOPs), and higher analogues having significant fluorescence quantum yields are covered.

3D-conjugated systems based on oligothiophenes and phosphorus nodes

3D-conjugated systems based on oligothiophene segments grafted on a phosphorus or on a phosphine oxide node have been synthesized. Under Stille coupling conditions, bromide terminated thienyl phosphine derivatives undergo a breaking of the phosphorus-carbon bond attributed to a ligand exchange with the Pd catalyst. The electronic properties of the new compounds have been analyzed by UV-vis and fluorescence spectroscopy and cyclic voltammetry.

Oxidative heck-type reaction involving cleavage of a carbon-phosphorus bond of arylphosphonic acids

Cleavage of a carbon-phosphorus bond is achieved under palladium catalysis in an oxidative Heck-type reaction which exploits arylphosphonic acids. The reaction of arylphosphonic acids with alkenes provides arylation products in good yields in the presence of TBAF with trimethylamine oxide as an oxidant.