Triboluminescence Phenomenon Based on the Metal Complex Compounds—A Short Review

Triboluminescence (TL) is a phenomenon of light emission resulting from the mechanical force applied to a substance. Although TL has been observed for many ages, the radiation mechanism is still under investigation. One of the exemplary compounds which possesses triboluminescent properties are copper(I) thiocyanate bipyridine triphenylphosphine complex [Cu(NCS)(py)2(PPh3)], europium tetrakis dibenzoylmethide triethylammonium EuD4TEA, tris(bipyridine)ruthenium(II) chloride [Ru(bpy)3]Cl2, and bis(triphenylphosphine oxide)manganese(II) bromide Mn(Ph3PO)2Br2. Due to the effortless synthesis route and distinct photo- and triboluminescent properties, these compounds may be useful model substances for the research on the triboluminescence mechanism. The advance of TL studies may lead to the development of a new group of sensors based on force-responsive (mechanical stimuli) materials. This review constitutes a comprehensive theoretical study containing available information about the coordination of metal complex synthesis methodologies with their physical, chemical, and spectroscopic properties.

Theoretical Study of Triphenylphosphine Oxide Derivatives for Blue Thermally Activated Delayed Fluorescence

We designed novel thermally activated delayed fluorescence (TADF) materials by combining the electron donor 10,10-diphenyl-5,10-dihydrodibenzo[b,e][1,4]azasiline (DDA) with the electron acceptor triphenylphosphine oxide (PO) unit (mDDA-PO and o-mDDA-PO) and compared their characteristics with those of a reference material using 1,3-Bis(N-carbazolyl)benzene (mCP) as an electron donor (mCP-PO) for blue organic light-emitting diodes (OLEDs). Using density functional theory (DFT) and time-dependent DFT calculations, we obtained the electron distributions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) as well as the energies of the lowest singlet (S1) and lowest triplet (T1) excited states. The calculated energy difference (ΔEST) between the S1 and T1 states of mDDA-PO (0.16 eV) and o-mDDA-PO (0.07 eV) were smaller than that of mCP-PO (0.48 eV). The results showed that o-mDDA-PO is a suitable blue OLED emitter because it has sufficiently small ΔEST values, which is favorable in a reverse-intersystem process crossing from the T1 state to S1 states, as well as an emission wavelength of 446.7 nm.

Functionalized triphenylphosphine oxide-based manganese(II) complexes for luminescent printing

Three novel neutral manganese(II) complexes (TPhPONMe2)2MnBr2, (TPhPOOMe)2MnBr2, and (TPhPOCF3)2MnBr2 have been designed and synthesized based on functionalized Ph3PO ligand. These structures are clarified by single crystal X-ray diffraction analysis, which...

Synthesis and Characterization of Eu3+ + 2-thenoyltrifluoroacetone + triphenylphosphine Oxide Ternary Complex

Rare earth europium ion (Eu3+) can emit red characteristic fluorescence under UV excitation and is preferred for the preparation of red phosphors for near-UV white LEDs. In this paper, the effects of solvent, reflux time and preparation method on the preparation of europium ternary complexes were studied with europium ion as the central coordination ion, 2-thenoyltrifluoroacetone as the first ligand and triphenylphosphine oxide as the second ligand. The results showed that the better reaction solvent was anhydrous ethanol and the better reflux time was 8 hours. Both the common synthesis method and the solvothermal method could successfully synthesize the europium ternary complex, and the solvothermal method has a higher yield. The europium ternary complex was characterized by inductively coupled plasma emission spectroscopy, element analysis and infrared spectroscopy, and it was proved that the europium complex could emit a strong characteristic red fluorescence of europium with the structure of Eu(TTA)3(TPPO)2 in 1:3:2 coordination ratio.