Joanna Palion-Gazda

This work is the study of the role of a remote amine substituent on the terpyridine ligand in controlling the photophysical and electroluminescent behavior of complexes [Ir(Ph-btz)₂(R-C₆H₄-terpy-κ²N)]PF₆. Introduction of the amine group into the Ph-terpy framework induced perturbations in the absorption and luminescent characteristics of [Ir(Ph-btz)₂(R-C₆H₄-terpy-κ²N)]PF₆ relative to the parent chromophores [Ir(Ph-btz)₂(terpy-κ²N)]PF₆ and [Ir(Ph-btz)₂(C₆H₅-terpy-κ²N)]PF₆. Consistent with the presence of vibronic structure, negligible emission solvatochromism, weak rigidochromic behavior, and substantial overlap with the phosphorescence of 2-phenylbenzothiazole, the emissive triplet excited state of the model complexes was assigned to ³IL_Ph-btz with a minor ³MLCT contribution. The amine-substituted Ir(III) complexes were found to exhibit altered emission characteristics, manifested by a structureless emission band impacted by the amine group and solvent polarity. It was rationalized by a switch from the ³IL_Ph-btz/MLCT excited state in model chromophores to a configurationally mixed ³ILCT/IL/MLCT_R-terpy in [Ir(Ph-btz)₂(R-C₆H₄-terpy-κ²N)]PF₆. With respect to the preliminary electroluminescence investigations, it was found that the introduction of the triphenylamine moiety enhances the stability of O/PEDOT/PSS/complex/Al devices. A deep insight into ground- and excited-state characters and photophysical properties of [Ir(Ph-btz)₂(R-C₆H₄-terpy-κ²N)]PF₆ was obtained by applying a wide range of experimental techniques, including cyclic voltammetry, UV-vis spectroscopy, photoluminescence spectroscopy, and transient absorption, complemented by DFT and TD-DFT calculations.

Transition metal complexes that can serve as photosensitizers (PSs) have attracted considerable scientific interest owing to their potential applications in photodynamic therapy (PDT), triplet-triplet annihilation for energy upconversion (TTA UC), photocatalysis, and time-resolved bioimaging techniques. In many of these applications, the efficiency of intermolecular triplet-triplet energy transfer (TTET) between the photosensitizer and acceptor is largely determined by the triplet excited-state lifetime of the photosensitizer. One of the most efficient strategies for extending the triplet lifetimes of transition metal complexes is the incorporation of organic chromophores possessing long-lived intraligand (³IL) excited states into the coordination sphere of transition metal complexes. Polycyclic aromatic hydrocarbons, particularly anthracene- and pyrene-based chromophores, have emerged as especially attractive building blocks for this purpose. The current contribution highlights the role of pyrene and anthracene groups in controlling the photophysical properties of cyclometalated iridium(III) metal complexes, with an emphasis on their applications as photosensitizers. Particular attention is devoted to elucidating the relationships between molecular structure and excited-state properties. A detailed discussion of these relationships has been performed for three classes of cyclometalated iridium(III) complexes: (1) charge-neutral Ir(III) complexes including pyrene and anthracene motifs, (2) cationic bis-cyclometalated iridium(III) complexes bearing pyrene-functionalized ligands, and (3) cationic mono- and bis-cyclometalated iridium(III) complexes bearing anthracene-functionalized ligands.

A series of cobalt(II) dicyanamide (dca⁻) coordination polymers with substituted pyrazines (pyz) and pyrimidines (pym) as auxiliary ligands have been synthesized and structurally characterized to investigate the influence of the type and substitution pattern of the auxiliary ligand on the dimensionality and topology of the resulting frameworks. As a result of our studies, 13 novel heteroleptic cobalt(II) dicyanamide coordination polymers were obtained, and their crystal structures were determined by single-crystal X-ray diffraction. Eight of the investigated compounds exhibit a single-chain structure composed of [Co(L_pyz/_pym)₂]²⁺ units bridged via double μ_1,5–dca ligands. In two complexes, neutral triple-chain topologies were observed, in which double μ_1,5– and single μ_1,3,5–dca bridges connect two crystallographically independent cobalt(II) ions, both being six-coordinate in tetragonally elongated octahedral environments. Two- and three-dimensional architectures were confirmed only in the case of Co(II) compounds with 2,6–Me₂pyz and 4-NH₂-pym co-ligand, respectively The cobalt(II) complexes described herein have also been compared with dicyanamide-based cobalt(II) systems incorporating pyrazine- and pyrimidine-like ligands. These structural relationships are of high significance for the rational design and synthesis of heteroleptic cobalt(II) dicyanamide systems.

Over the last nine decades, 2,2′:6′,2″-terpyridine (terpy) derivatives and their transition d-metal complexes have been extensively explored due to their unique and widely tuned optical, electrochemical, and biological properties. Terpyridyl transition metal complexes occupy a prominent position among functional molecular materials for applications in optoelectronics, life science, catalysis, and photocatalysis, as well as they have played a key role in determining structure–property relationships. This review summarizes the developments of amine-functionalized R-C₆H₄-terpy systems and their d-metal complexes, largely concentrating on their photophysical and electrochemical properties. Functionalization of the terpy core with the electron-rich group, attached to the central pyridine ring of the terpy backbone via the phenylene linker, gives rise to organic push–pull systems showing the photoinduced charge flow process from the peripheral donor substituent to the terpy acceptor. The introduction of amine-functionalized R-C₆H₄-terpy systems into the coordination sphere of a d-metal ion offers an additional way for controlling the photophysics of these systems, in agreement with the formation of the excited state of intraligand charge transfer (ILCT) nature. Within this review, a detailed discussion has been presented for R-C₆H₄-terpys modified with acyclic and cyclic amine groups and their Cr(III), Mn(I), Re(I), Fe(II), Ru(II), Os(II), Pt(II), and Zn(II) coordination compounds.

The latest developments in controlling the photoinduced processes of Re(i) tricarbonyl complexes bearing D–A and D–π–A ligands with six different diimine cores decorated by various electron-rich amine, sulphur-based and π-conjugated aryl groups.

This paper provides extensive studies of [IrCl(Ph-py)(morph-C₆H₄-terpy-κ³N)]PF₆ (1A), [Ir(Ph-py)₂(morph-C₆H₄-terpy-κ²N)]PF₆ (2A), [IrCl(Ph-py)(Ph-terpy-κ³N)]PF₆ (1B), and [Ir(Ph-py)₂(Ph-terpy-κ²N)]PF₆ (2B) designed to demonstrate the possibility of controlling the photophysical properties of mono- and bis-cyclometalated complexes [IrCl(Ph-py)(R-C₆H₄-terpy-κ³N)]PF₆ and [Ir(Ph-py)₂(R-C₆H₄-terpy-κ²N)]PF₆ through a remote electron-donating substituent introduced into the 4'-position of 2,2':6',2″-terpyridine (terpy) via the phenyl linker. The attachment of the morpholinyl (morph) group was evidenced to induce dramatic changes in the emission characteristics of the monocyclometalated Ir(III) systems with meridionally coordinated R-C₆H₄-terpy ligand (κ³N). In solution, the obtained complex [IrCl(Ph-py)(morph-C₆H₄-terpy-κ³N)]PF₆ was found to be a rare example of dual-emissive Ir(III) systems. Within the series [Ir(Ph-py)₂(R-C₆H₄-terpy-κ²N)]PF₆ bearing the R-C₆H₄-terpy ligand bound to the central ion in a bidentate coordination mode, the appended electron-donating morpholinyl group induced a minor effect on the emission maximum, but it was found to be an effective tool for extending the excited-state lifetime, further prolonging with the increase of solvent polarity. The results of this work are of high significance for better understanding the push-pull effect and dual-emission phenomena in Ir-based luminophores, as well as developing chromophores with prolonged emission lifetimes.

To investigate the impact of the electron-donating morpholinyl (morph) group on the ground- and excited-state properties of two different types of Ir(III) complexes, [IrCl₃(R-C₆H₄-terpy-κ³N)] and [Ir(R-C₆H₄-terpy-κ³N)₂](PF₆)₃, the compounds [IrCl₃(morph-C₆H₄-terpy-κ³N)] (1A), 4[Ir(morph-C₆H₄-terpy-κ³N)₂](PF₆)₃ (2A), [IrCl₃(Ph-terpy-κ³N)] (1B) and [Ir(Ph-terpy-κ³N)₂](PF₆)₃ (2B) were obtained. Their photophysical properties were comprehensively investigated with the aid of static and time-resolved spectroscopic methods accompanied by theoretical DFT/TD-DFT calculations. In the case of bis-terpyridyl iridium(III) complexes, the attachment of the morpholinyl group induced dramatic changes in the absorption and emission characteristics, manifested by the appearance of a new, very strong visible absorption tailing up to 600 nm, and a significant bathochromic shift in the emission of 2A relative to the model chromophore. The emission features of 2A and 2B were found to originate from the triplet excited states of different natures: intraligand charge transfer (³ILCT) for 2A and intraligand with a small admixture of metal-to-ligand charge transfer (³IL–³MLCT) for 2B. The optical properties of the mono-terpyridyl iridium(III) complexes were less significantly impacted by the morpholinyl substituent. Based on UV–Vis absorption spectra, emission wavelengths and lifetimes in different environments, transient absorption studies, and theoretical calculations, it was demonstrated that the visible absorption and emission features of 1A are governed by singlet and triplet excited states of a mixed MLLCT-ILCT nature, with a dominant contribution of the first component, that is, metal-ligand-to-ligand charge transfer (MLLCT). The involvement of ILCT transitions was reflected by an enhancement of the molar extinction coefficients of the absorption bands of 1A in the range of 350–550 nm, and a small red shift in its emission relative to the model chromophore.

This is the first comprehensive review of rhenium(I) carbonyl complexes with 2,2′:6′,2″-terpyridine-based ligands (R-terpy)—encompassing their synthesis, molecular features, photophysical behavior, and potential applications. Particular attention has been devoted to demonstrating how the coordination mode of 2,2′:6′,2″-terpyridine (terpy-κ²N and terpy-κ³N), structural modifications of terpy framework (R), and the nature of ancillary ligands (X—mono-negative anion, L—neutral ligand) may tune the photophysical behavior of Re(I) complexes [Re(X/L)(CO)₃(R-terpy-κ²N)]^0/+ and [Re(X/L)(CO)₂(R-terpy-κ³N)]^0/+. Our discussion also includes homo- and heteronuclear multicomponent systems with {Re(CO)₃(R-terpy-κ²N)} and {Re(CO)₂(R-terpy-κ³N)} motifs. The presented structure–property relationships are of high importance for controlling the photoinduced processes in these systems and making further progress in the development of more efficient Re-based luminophores, photosensitizers, and photocatalysts for modern technologies.

To get a better insight into understanding the factors affecting the enhancement of the magnetic anisotropy in single molecule (single ion) magnets, two cobalt(II) complexes based on a tridentate ligand 2,6-di(thiazol-2-yl)pyridine substituted at the 4-position with N-methyl-pyrrol-2-yl have been synthesized and studied by X-ray crystallography, AC and DC magnetic data, FIRMS and HFEPR spectra, and theoretical calculations. The change of the counteranion in starting Co(II) salts results in the formation of pentacoordinated mononuclear [Co(mpyr-dtpy)Cl₂]·2MeCN (1) complex and binuclear [Co(mpyr-dtpy)₂][Co(NCS)₄] (2) compound. The observed marked distortion of trigonal bipyramid geometry in 1 and cationic octahedral and anionic tetrahedral units in 2 brings up a question about the validity of the spin-Hamiltonian formalism and the possibility of determining the value and sign of the zero-field splitting D parameter. Both complexes exhibit field-induced slow magnetic relaxation with two or three relaxation channels at B_DC = 0.3 T. The high-frequency relaxation time in the reciprocal form τ(HF)^-1 = CTⁿ develops according to the Raman relaxation mechanism (for 2, n = 8.8) and the phonon-bottleneck-like mechanism (for 1, n = 2.3). The high-frequency relaxation time at T = 2.0 K and B_DC = 0.30 T is τ(HF) = 96 and 47 μs for 1 and 2, respectively.