Modulation of the Excited States of Ruthenium(II)-perylene Dyad to Access Near-IR Luminescence, Long-Lived Perylene Triplet State and Singlet Oxygen Photosensitization

Herein, we present a novel ruthenium(II)-perylene dyad (RuPDI-Py) that combines the photophysical properties of pyrrolidine-substituted perylene diimide (PDI-Py) and the ruthenium(II) polypyridine complex [Ru(phen)3]2+. A comprehensive study of excited-state dynamics was carried out using time-resolved and steady-state methods in a dimethyl sulfoxide solution. The RuPDI-Py dyad demonstrated excitation wavelength-dependent photophysical behavior. Upon photoexcitation above 600 nm, the dyad exclusively exhibits the near-infrared (NIR) fluorescence of the 1PDI-Py state at 785 nm (τfl = 1.50 ns). In contrast, upon photoexcitation between 350 and 450 nm, the dyad also exhibits a photoinduced electron transfer from the {[Ru(phen)3]2+} moiety to PDI-Py, generating the charge-separated intermediate state {Ru(III)-(PDI-Py)•-} (4 μs). This state subsequently decays to the long-lived triplet excited state 3PDI-Py (36 μs), which is able to sensitize singlet oxygen (1O2). Overall, tuning 1O2 photoactivation or NIR fluorescence makes RuPDI-Py a promising candidate for using absorbed light energy to perform the desired functions in theranostic applications.

Luminescence and Palladium: The Odd Couple

The synthesis, photophysical properties, and applications of highly fluorescent and phosphorescent palladium complexes are reviewed, covering the period 2018–2022. Despite the fact that the Pd atom appears closely related with an efficient quenching of the fluorescence of different molecules, different synthetic strategies have been recently optimized to achieve the preservation and even the amplification of the luminescent properties of several fluorophores after Pd incorporation. Beyond classical methodologies such as orthopalladation or the use of highly emissive ligands as porphyrins and related systems (for instance, biladiene), new concepts such as AIE (Aggregation Induced Emission) in metallacages or in coordination-driven supramolecular compounds (CDS) by restriction of intramolecular motions (RIM), or complexes showing TADF (Thermally Activated Delayed Fluorescence), are here described and analysed. Without pretending to be comprehensive, selected examples of applications in areas such as the fabrication of lighting devices, biological markers, photodynamic therapy, or oxygen sensing are also here reported.

A novel AB3-type trimeric zinc(II)-phthalocyanine as an electrochromic and optical limiting material

Recent advances in the practical applications of metallophthalocyanines (MPcs) in different technological fields have stimulated us to design and synthesize a new asymmetric AB3-type trimeric zinc(ii)-phthalocyanine (1). This bulky and high molecular weight compound was characterized by elemental analysis, 1H, 13C DEPT, and 1H-1H NOESY NMR, HR MALDI-TOF mass spectrometry, UV-vis, and FT-IR (ATR) techniques. In-depth electrochemical studies show that 1 displays quasi-reversible three one-electron reductions and two one- or two-electron oxidation processes, rather than any redox processes including the transfer of three-electrons in one-step. Besides this, in situ spectroelectrochemical measurements suggest the good application potential of 1 as an electrochromic material in display technologies. A study of the nonlinear optical properties (NLOs) of 1 reveals that the poly(methylmethacrylate) (PMMA) composite film displays a much larger nonlinear absorption coefficient and a lower saturable absorption threshold for optical limiting when compared to the same Pc molecules in solution. Ultrafast transient absorption measurements reveal the intersystem crossing mechanism. Density functional theory (DFT) was used for the geometry optimizations and time dependent-DFT (TD-DFT) for HOMO/LUMO energies and electronic transitions for 1.

Rhenium (I) Complexes as Probes for Prokaryotic and Fungal Cells by Fluorescence Microscopy: Do Ligands Matter?

Re(I) complexes have exposed highly suitable properties for cellular imaging (especially for fluorescent microscopy) such as low cytotoxicity, good cellular uptake, and differential staining. These features can be modulated or tuned by modifying the ligands surrounding the metal core. However, most of Re(I)-based complexes have been tested for non-walled cells, such as epithelial cells. In this context, it has been proposed that Re(I) complexes are inefficient to stain walled cells (i.e., cells protected by a rigid cell wall, such as bacteria and fungi), presumably due to this physical barrier hampering cellular uptake. More recently, a series of studies have been published showing that a suitable combination of ligands is useful for obtaining Re(I)-based complexes able to stain walled cells. This review summarizes the main characteristics of different fluorophores used in bioimage, remarking the advantages of d⁶-based complexes, and focusing on Re(I) complexes. In addition, we explored different structural features of these complexes that allow for obtaining fluorophores especially designed for walled cells (bacteria and fungi), with especial emphasis on the ligand choice. Since many pathogens correspond to bacteria and fungi (yeasts and molds), and considering that these organisms have been increasingly used in several biotechnological applications, development of new tools for their study, such as the design of new fluorophores, is fundamental and attractive.

Syntheses and studies of electron/energy transfer of new dyads based on an unsymmetrical perylene diimide incorporating chelating 1,10-phenanthroline and its corresponding square-planar complexes with dichloroplatinum(ii) and dichloropalladium(ii )

Photophysical properties of new dyads have been studied with steady-state absorption and TDDFT.