Search Results (163)

Terpyridines are well-known ligands in coordination chemistry, are valued for their conformational flexibility and strong metal-binding properties, and are also of interest as fluorophores. This study focused on the synthesis and comprehensive investigation of a new class of bis-oxazolo[5,4-b]pyridine derivatives, designed based on their structural similarity to terpyridines. Four novel compounds, 4a–d, were synthesized by cyclization of amide derivatives of 3-aminopyridin-2(1H)-ones using pyridine-2,6-dicarboxylic acid and its dichloride as key acidic components. Their structures and purity were confirmed by melting point analysis, high-resolution mass spectrometry, and ¹H, ¹³C NMR spectroscopy. Compounds 4a–c exhibit UV absorption at 323–357 nm and intense blue to deep-blue fluorescence (357–474 nm, цi ≈ 0.32–0.84) in chloroform, dichloromethane, and acetonitrile, attributed to p–p* transitions within the conjugated ring system. These findings suggest their potential as phosphors for organic electronics. Computational modeling of 4a–c molecules provided insight into their electronic structures, conformational stability, and predicted optical behavior. The most stable conformers (4a–II, 4b–II, 4c–II′) exhibited a progressive decrease in the HOMO–LUMO gap from 4a to 4c, correlated with the enhancement of photoactivity. Among them, compound 4a stands out as the most promising luminophore, displaying the most intense and narrow luminescence band, owing to its high molecular symmetry and stable emission characteristics. Overall, this study lays the foundation for future studies of bis(oxazolo[5,4-b]pyridine) derivatives in coordination chemistry and optoelectronic materials development. Full article

Copper(II) complexes with 2,2′:6′,2″-terpyridines (terpys) are promising candidates for anticancer therapy and catalysis. Their structural and optical properties can be tuned by modifying the terpy backbone, including a substitution at the 4′ position or the replacement of peripheral pyridines with thiazole rings, forming 2,6-bis(thiazol-2-yl)pyridines (dtpys). dtpy-based copper(II) complexes (Cu-dtpys), despite their applicative potential, are barely characterized in the literature. Here, the series of Cu-dtpys (1–13) was synthesised and characterized by FT-IR, HRMS, X-ray diffraction, and UV-Vis spectroscopy. Their structural and optical features were compared to previously studied Cu-dtpys (14–24) and their terpy analogues (Cu-terpy-1 ÷ Cu-terpy-24). The detailed analysis revealed that five-coordinate Cu-dtpys complexes adopt a square pyramidal geometry comparable to that of Cu-terpys complexes but with markedly smaller deviations from the ideal square pyramid. Compared with Cu-terpys, Cu–Cl_apical bonds are shorter, while Cu–N_central bonds are elongated. The Cu-dtpy systems usually present the longest wavelength of the lowest energy absorption band in comparison to Cuterpys. The analysis of the relationship between Hammett’s constant and wavelength of absorption indicates that the most promising from the photophysical point of view are compounds 4–6, 10–13, 16–17, and 22, for which a newly formed intraligand charge transfer band is formed. Full article

The osmium(II) polypyridyl complex [Os(tpy)(pydppn)]²⁺ (tpy = 2,2′:6′,2″-terpyridine; pydppn = 3-(pyrid-2′-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene) was synthesized and characterized to evaluate the effect of an extended planar π-system on photophysical properties and DNA interactions. This complex represents the π-expanded analog of the previously studied [Os(tpy)(pydppz)]²⁺ system. Electrochemical studies revealed a reversible Os(II)/Os(III) oxidation at +0.99 V vs. SCE and five ligand-centered reductions, generally less negative than those of the smaller pydppz analog, consistent with enhanced electron-accepting ability. In acetonitrile, the complex exhibits UV absorption bands at 328 and 473 nm and near-infrared emission at 840 nm, assigned to a long-lived ³MLCT state (τ = 110 ns, Φ = 0.02). Upon titration with calf-thymus DNA, [Os(tpy)(pydppn)]²⁺ shows a pronounced light-switch effect, hypochromism, red-shifted MLCT bands, induced circular dichroism, and an increase in DNA melting temperature (ΔT_m = 8.9 ± 0.5 °C), consistent with intercalative binding. Viscometric titrations further support intercalation, with a binding constant K_B ≈ 1.2 × 10⁶ M⁻¹. Transient absorption spectroscopy indicates that DNA binding prolongs the excited-state lifetime and modifies vibrational relaxation pathways. These results highlight how π-system extension in Os(II) complexes modulates photophysical behavior and DNA affinity, offering insights for the rational design of NIR-emitting, DNA-targeted luminescent probes and potential phototherapeutic agents. Full article

Three new terpyridine derivatives which contain a pendant furan heterocycle have been prepared and characterized. The first two, 4′-(4,5-dimethylfuran-2-yl)-2,2′:6′,2″-terpyridine (1) and 4′-((1,3-dioxolan-2-yl)furan-2-yl)-2,2′:6′,2″-terpyridine (2), are obtained through the reaction of 2-acetylpyridine and suitable furaldehydes using the Kröhnke reaction. The last one, 4′-(5-formylfuran-2-yl)-2,2′:6′,2′’-terpyridine (3) is obtained via acidic hydrolysis of the acetal onto terpyridine (2). The structures of these new compounds are confirmed using different analytical techniques such as NMR and infrared spectroscopy (ATR-IR) as well as by High Resolution Mass Spectrometry (HRMS). Full article

Prostate cancer (PCa), particularly in its metastatic form, remains a major clinical challenge due to limited diagnostic and therapeutic options. To address this, we developed a novel radiotheranostic agent, [⁶⁴Cu]Cu-NOTA-TP-PSMA, by conjugating a prostate-specific membrane antigen (PSMA) ligand to a ⁶⁴Cu-radiolabeled terpyridine-platinum (TP) compound previously shown to exert selective cytotoxicity against cancer cells. In this study, the biological performance of [⁶⁴Cu]Cu-NOTA-TP-PSMA was compared with the monomeric analogs [⁶⁴Cu]Cu-NOTA-PSMA and [⁶⁴Cu]Cu-NOTA-TP through in vitro studies in PSMA-positive LNCaP prostate cancer cells and non-malignant HEK-293 cells. [⁶⁴Cu]Cu-NOTA-TP-PSMA showed high stability, PSMA binding affinity and exhibited substantially enhanced uptake, internalization, retention, and nuclear localization in LNCaP cells relative to the monomers, whereas uptake and nuclear accumulation in HEK-293 cells were negligible. Cytotoxicity assays further demonstrated potent and selective activity in LNCaP cells, with EC₅₀ values in the low nanomolar range, and minimal toxicity in HEK-293 cells. Collectively, these results identify [⁶⁴Cu]Cu-NOTA-TP-PSMA as a promising radiotheranostic agent, warranting further in vivo evaluation for prostate cancer imaging and targeted radiotherapy. Full article

Redox-active manganese, iron, and nickel complexes of pyridin-2-ylsulfonyl-quinolin-8-yl-amide (psq) provide information for assessing the electronic and structural properties of this new tridentate ligand. Single-crystal X-ray structures show that psq coordinates in a meridional mode with a trigonal geometry for the central deprotonated sulfonamide N donor. With the structures described here, there are now five structures known for hexacoordinated bis-homoleptic complexes of psq. All show the same geometry. No fac isomer, although feasible, has been structurally characterized. The geometrical parameters for [M(psq)₂]^0/+ are surprisingly close to those for archetypical [M(terpy)₂]^2+/3+ (terpy =2,2′:6′,2″-terpyridine) complexes, with octahedral distortion parameters indicating a geometry that is slightly closer to a regular octahedral. The Fe(II) complex, however, bucks this trend, consistent with the magnetic susceptibility measurements indicating a high-spin S = 5/2 state, which stands in contrast to low-spin [Fe(terpy)₂]²⁺. This is rationalized by the trans secondary sulfonamide donors being weaker π acceptors compared to central terpy pyridine donors. An overall two-integer reduced charge for the complexes is consistent with the Co^II/Co^I, M^III/M^II M = Mn, Fe, Co, and Mn^IV/Mn^III redox events being ca. 600–900 mV more cathodic compared to the corresponding events for [M(terpy)₂]²⁺. Full article

Glioblastoma multiforme (GBM) remains one of the most aggressive and treatment-resistant brain tumors, with poor prognosis and limited therapeutic options. Background/Objectives: Integrin α_vβ₃, a cell surface receptor overexpressed in GBM, specifically binds to cyclic arginine-glycine-aspartate-D-phenylalanine-lysine (c(RGDfK)) motif, making it a valuable target for tumor-specific delivery and PET imaging. This study explores a novel radiotheranostic agent, [⁶⁴Cu]Cu-NOTA-TP-c(RGDfK), which combines the imaging and therapeutic capabilities of copper-64 (⁶⁴Cu) and the cytotoxic activity of a terpyridine-platinum (TP) complex, conjugated to c(RGDfK). Methods: A robust protocol was developed for the small-scale preparation of NOTA-TP-c(RGDfK). Comparative cellular studies were conducted using U87 MG glioblastoma (GBM) cells and SVG p12 human astrocytes to evaluate the performance of [⁶⁴Cu]Cu-NOTA-TP-c(RGDfK) relative to [⁶⁴Cu]Cu-NOTA-c(RGDfK), [⁶⁴Cu]Cu-NOTA-TP, ^natCu-NOTA-TP-c(RGDfK), cisplatin, and temozolomide. Results: ⁶⁴Cu-radiolabeling of NOTA-TP-c(RGDfK) was achieved with >99% radiochemical purity, and competition assays confirmed high binding affinity to integrin α_vβ₃ (IC₅₀ = 16 ± 8 nM). Cellular uptake, internalization, and retention studies demonstrated significantly higher accumulation of [⁶⁴Cu]Cu-NOTA-TP-c(RGDfK) in U87 MG cells compared to control compounds, with 38.8 ± 1.8% uptake and 28.0 ± 1.0% internalization at 24 h. Nuclear localization (6.0 ± 0.5%) and stable intracellular retention further support its therapeutic potential for inducing localized DNA damage. Importantly, [⁶⁴Cu]Cu-NOTA-TP-c(RGDfK) exhibited the highest cytotoxicity in U87 MG cells (IC₅₀ = 10 ± 2 nM at 48 h), while maintaining minimal toxicity in normal SVG p12 astrocytes. Conclusions: These results highlight [⁶⁴Cu]Cu-NOTA-TP-c(RGDfK) as a promising targeted radiotheranostic agent for GBM, warranting further preclinical development Full article

The intermediate compound 4′-phenyl-1′,4′-dihydro-2,2′:6′,2″-terpyridine (pdhtpy) was isolated for the first time during the synthesis of 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) and characterised by single-crystal X-ray diffraction. Pdhtpy crystallises in the triclinic crystal system with space group P$\bar{1}$ with the following unit cell parameters at 100 K: a = 6.1325(4) Å; b = 8.2667(5) Å; c = 16.052(2) Å; α = 86.829(2)°; β = 82.507(2)°; γ = 84.603(2)°; V = 802.49(9) ų. The absence of stabilising electron-withdrawing groups renders pdhtpy prone to oxidative conditions. Pdhtpy was obtained as a mixture with ptpy, confirmed by Rietveld refinement of the powder X-ray diffraction pattern. Notably, pdhtpy is the first solid-state 1,4-dihydropyridine lacking electron-withdrawing groups at both positions 3 and 5, distinguishing it from Hantzsch esters and related compounds. Full article

The detection of zinc ions plays an essential role in protecting public health and maintaining ecological balance. However, traditional fluorescent probes for Zn²⁺ are limited in their specificity, especially under complex environments, due to their single-mode optical signal and inadequate recognization capacities. Herein we report a dual-mode supramolecular sensing system constructed from a unique three-component assembly involving a terpyridine platinum (II) complex, oxalate, and Zn²⁺, enabling highly specific detection performance for Zn²⁺. The supramolecular sensing system exhibits excellent selectivity among various interfering substances, accompanied by ultra-low detection limit (0.199 μM) and fast response (<3 s). The high recognization capacity comes from tri-component-based supramolecular assembly, while the dual-mode response arises from the generation of intermelcular Pt-Pt and π-π interactions, which yields absorption and emission originating from low-energy metal–metal-to-ligand charge transfer (MMLCT) transitions. This work marks a pioneering demonstration for highly specific detection of Zn²⁺ and inspires an alternative strategy for designing cation probes. Full article

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. Full article

Coordination polymers are attractive materials for various fields of practical application. The high degree of freedom of choice of metal ions and organic ligands plays a critical role in functional diversification. In the present study, we report the liquid–liquid interfacial synthesis of a 2D bis(terpyridine)copper(II) polymer thin film, Cu-tpy. The synthesized Cu-tpy was characterized by various microscopic observations such as TEM, SEM, and AFM, and spectroscopic measurements such as XPS, Raman spectroscopy, SEM/EDS, and UV–Vis spectroscopy. Synchrotron-radiated X-ray scattering confirmed that Cu-tpy was oriented crystalline films. Moreover, Cu-tpy showed electrochemical micro-supercapacitor behavior in the solid-state owing to its ionic nature. This study expands the potential of bis(terpyridine)metal(II) polymers as electro-functional materials. Full article

An asymmetric two-arm polypyridine ligand 4′-{4-[4-(2,2′-dipyridyl)phenyl]}-2,2′:6′,2′-terpyridine (TPY-Ph-BPY) with double coordination units was synthesized using the one-step Suzuki reaction. The metallic supramolecular film was subsequently obtained by the Fe²⁺-induced self-assembly method at the CHCl₃-H₂O interface, which displayed a distinct flat and continuous morphology. The supramolecular film-coated ITO electrode demonstrated a reversible electrochemical redox behavior with pronounced color changes between purple and light green. Its solid-state electrochromic device had an optical contrast (ΔT%) of 26.2% at λ_max = 573 nm with balanced coloring (t_c = 2.4 s) and bleaching (t_b = 2.6 s) times and a high current efficiency of 507.8 cm²/C. Moreover, good cycling stability with a long-term reversible color change was observed beyond 900 cycles. These results suggested the promising potential of the TPY-Ph-BPY-Fe(II) supramolecular film for electrochromic applications. Full article