New phosphorescent platinum(ii) complexes: lamellar mesophase and mechanochromism

Abstract

Several new square planar platinum(ii) complexes based on modified 2-phenylpyridine derivatives as the main ligand and picolinic acid as the auxiliary ligand were synthesized and their photophysical properties, and mechanochromic and liquid crystalline behavior were investigated.

Enhanced Synchronously Emission Dissymmetry Factor and Quantum Efficiency of Circularly Polarized Phosphorescence from Point-Chiral Cyclometalated Platinum(II) Liquid Crystal

“…The intensive absorptions between 240 and 375 nm are assigned to the spin-allowed ligand electronic transition ( 1 ILCT, 1 π–π*) from the ligand centers of the 2-phenylpyridine derivatives and the picolinic acid auxiliary ligand. The lowest energy absorption band was observed at 375–450 nm, which was attributed to metal-to-ligand charge transfer (MLCT). , Figure a shows the photoluminescence (PL) spectra of the ( S )-Pt-L1 complexes in DCM solution (10 –5 mol L –1 ), liquid crystal, and solid powder state at room temperature. The emission spectra of Pt-L1 in DCM solution display the vibrational structure with maximum values at 508 nm and a shoulder at 531 nm at room temperature, respectively.…”

“…The lowest energy absorption band was observed at 375−450 nm, which was attributed to metal-to-ligand charge transfer (MLCT). 67,68 Figure 3a shows the photoluminescence (PL) spectra of the (S)-Pt-L1 complexes in DCM solution (10 −5 mol L −1 ), liquid crystal, and solid powder state at room temperature. The emission spectra of Pt-L1 in DCM solution display the vibrational structure with maximum values at 508 nm and a shoulder at 531 nm at room temperature, respectively.…”

Advanced Functional Luminescent Metallomesogens: The Key Role of the Metal Center

“…88−92 However, the impact of metallomesogens in this area is less developed although they are good candidates by combining the ordered and fluid states of the liquid crystal phases with the luminescent properties induced by the metal center. 86,87,89 The research of mononuclear Ln(III)-metallomesogens has been carried out from ligands as Schiff bases, β-diketonate, bis(benzylimidazolyl)pyridine, pyridone, or macrocycles. 93,94 These species show smectic and/or columnar mesophases with relatively high melting temperatures (190−240 °C).…”

“…Another wide field of application for metallomesogens is the development of chromoactive materials, which currently have attracted high interest due to their potential usefulness in the fabrication of sensors, data recording devices, and encryption systems, among others. − Luminescent emission in metallomesogens, in which lamellar or columnar molecular self-assemblies are favored, causes variations in the HOMO and LUMO orbitals, and therefore also in their photophysical behavior. Thus, modifications in the molecular structure, although they could be small, can modify or induce molecular interactions, originating changes in the luminescence emission or even responses to certain external stimuli.…”

“…Thus, modifications in the molecular structure, although they could be small, can modify or induce molecular interactions, originating changes in the luminescence emission or even responses to certain external stimuli. The influence of external stimuli on the luminescent emission of these materials, both in the solid state and in the mesophase, opens up new possibilities for their considering as chromoactive materials and, consequently, for their application as sensors to detect temperature and/or pressure changes, pollutant metal ions, acidic media of different strength, among others. , Chromoactive materials based on crystalline compounds, polymers, and LC materials are known. − However, the impact of metallomesogens in this area is less developed although they are good candidates by combining the ordered and fluid states of the liquid crystal phases with the luminescent properties induced by the metal center. ,, …”