Remarkably flexible 2,2′:6′,2″-terpyridines and their group 8–10 transition metal complexes – Chemistry and applications

Anti-cancer property and DNA binding interaction of first row transition metal complexes: A decade update

Metal ions carry out a wide variety of functions, including acid-base/redox catalysis, structural functions, signaling, and electron transport. Understanding the interactions of transition metal complexes with biomacromolecules is essential for biology, medicinal chemistry, and the production of synthetic metalloenzymes. After the coincidental discovery of cisplatin, importance of the metal complexes in biochemistry became a top priority for inquiry. In this review, a decade update on various synthetic strategies to first row transition metal complex and their interaction with DNA through non-covalent binding are explored. Moreover, this effort provides an excellent analysis on the efficacy of theoretical and practical approaches to the systematic generation of new non-platinum based metallodrugs for anti-cancer therapeutics.

Exploring the binding properties of DNA/BSA and cytotoxicity studies with new terpyridine-ester-based metal complexes (M = Fe(III), Ni(II), Cu(II) and Ru(III)) - A comparative analysis

Many terpyridines and their metal complexes are known to exhibit remarkable potential for the interaction of biological targets. Notably, a subtle change in the structure of the ligand can influence these interactions significantly. In this regard, it would be very interesting to assess the binding affinity of functionalized molecules with DNA/BSA. In this work, a novel ester-based terpyridine (L) and the corresponding four metal complexes with Ni(II) (MC1), Cu(II) (MC2), Fe(III) (MC3) and Ru(III) (MC4) were prepared and structurally characterized using various spectroscopic and analytical techniques including the validation of molecular structures of ligand (L) and Ni(II)-Tpy complex (MC1). The EPR data demonstrate that MC1 is diamagnetic and other complexes (MC2-MC4) exhibit paramagnetic behavior. Additionally, the structures of ligands and metal complexes were determined using DFT studies and the same were utilized for the docking studies. Interestingly, MC3 and MC4 exhibit a predominant lowest binding energy of -9.62 Kcal/mol (with DNA) and -10.05 Kcal/mol (with BSA) respectively. The binding affinity of the ligand and its complexes with protein and DNA was evaluated by spectroscopic techniques. Notably, the cytotoxicity studies of L and MC1-MC4 were performed against the MCF-7 (human breast cancer) cell lines. The complex MC4 displayed great activity with an IC50 of 3.5 ± 1.75 μM among all synthesized compounds and comparable with cisplatin.

Studies on synthesis and influence of sterically driven Ni(II)-terpyridine (NNN) complexes on BSA/DNA binding and anticancer activity

The present work demonstrates the synthesis, structural diversity and coordination behavior of some selected new Ni(II)-Tpy complexes. The structural analysis revealed the coordination of the selected terpyridine ligands with the core metal atom in two different modes via dimeric species (1:1 fashion) through the Cl-bridging and a bis(Tpy)-Ni complex (2:1 fashion). Perhaps the most striking manifestations of these Ni(II)-Tpy complexes are BSA/DNA binding ability and anticancer activity. In addition, the cytotoxicity studies of Tpy ligand (4-([2,2':6',2″-terpyridin]-4'-yl)phenyl 5-methylthiophene-2-carboxylate) and the Ni(II) complexes were carried out using lung cancer cell line (A549), breast cancer cell line (MCF-7) and normal cell line (Vero cell). The cytotoxicity results were compared with the cisplatin control group. Notably, bis-terpyridyl complex 3C (R = 4-([2,2':6',2″-terpyridin]-4'-yl)phenyl 4-isopropoxybenzoate) demonstrates better activity with the IC50 value of 23.13 ± 3 μm for A549 and 22.7 ± 3 for MCF-7. The DFT calculations reveal the significant energy differences of HOMO and LUMO for the ligands and their corresponding Ni(II) complexes. The Tpy ligands and Ni(II)-Tpy complexes were investigated for BSA binding and further all the Ni(II) complexes were analyzed for DNA binding studies.

Terpyridine-Decorated Polymer Nanosphere Latex: Template Nanocarriers for the Synthesis of Cu-CeO2 Hollow Spheres

Water-soluble polymers with the ability to complex metal ions through complexing ligands have attracted significant interest in diverse domains, such as optical or catalyst applications. In this paper, we successfully synthesized, through a one-pot process combining polymerization-induced self-assembly and reversible addition-fragmentation chain transfer polymerization, aqueous dispersions of terpyridine-decorated poly[poly(ethylene glycol)methyl ether methacrylate]-b-poly(methyl methacrylate) (tpy-PPEGMA-b-PMMA) amphiphilic block copolymers. The in-situ formation of well-defined amphiphilic block copolymers and their self-assembly led to nanosphere latex with the hydrodynamic diameters increasing from 17 to 52 nm and the length of the copolymers increasing from 21,000 to 51,000 g·mol-1. These aqueous dispersed tpy-PPEGMA-b-PMMA nanospheres effectively complex metal ions, such as Cu2+, in a stoichiometric ratio of 2:1. Subsequently, these metal-complexed nanospheres were employed as soft template nanocarriers to control, on the nanometer scale, the dispersion of metal on a nanostructured support. This is exemplified by the synthesis of copper supported on cerium oxide hollow spheres (Cu-CeO2) using Cu2+-tpy-PPEGMA-b-PMMA as template nanocarriers and CeO2 nanoparticles. This novel assembly engineering strategy for the preparation of atomically dispersed metal on a nanostructured support was highlighted through the utilization of Cu-CeO2 hollow spheres as an electrocatalyst for the nitrate reduction reaction (NO3RR) to NH3. These encouraging outcomes emphasize the potential of metal-metal oxide-nanostructured materials to treat contaminated water sources with nitrate while allowing the green production of ammonia.

Recent developments in the synthesis and applications of terpyridine-based metal complexes: a systematic review

Terpyridine-based metal complexes have emerged as versatile and indispensable building blocks in the realm of modern chemistry, offering a plethora of applications spanning from materials science to catalysis and beyond. This comprehensive review article delves into the multifaceted world of terpyridine complexes, presenting an overview of their synthesis, structural diversity, and coordination chemistry principles. Focusing on their diverse functionalities, we explore their pivotal roles in catalysis, supramolecular chemistry, luminescent materials, and nanoscience. Furthermore, we highlight the burgeoning applications of terpyridine complexes in sustainable energy technologies, biomimetic systems, and medicinal chemistry, underscoring their remarkable adaptability to address pressing challenges in these fields. By elucidating the pivotal role of terpyridine complexes as versatile building blocks, this review provides valuable insights into their current state-of-the-art applications and future potential, thus inspiring continued innovation and exploration in this exciting area of research.

The Role of Intraligand Charge Transfer Processes in Iridium(III) Complexes with Morpholine-Decorated 4'-Phenyl-2,2':6',2″-terpyridine

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.

Synthesis, characterization and structural analysis of complexes from 2,2':6',2''-terpyridine derivatives with transition metals

The synthesis and structural characterization of three families of coordination complexes synthesized from 4'-phenyl-2,2':6',2''-terpyridine (8, Ph-TPY), 4'-(4-chlorophenyl)-2,2':6',2''-terpyridine (9, ClPh-TPY) and 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine (10, MeOPh-TPY) ligands with the divalent metals Co2+, Fe2+, Mn2+ and Ni2+ are reported. The compounds were synthesized from a 1:2 mixture of the metal and ligand, resulting in a series of complexes with the general formula [M(R-TPY)2](ClO4)2 (where M = Co2+, Fe2+, Mn2+ and Ni2+, and R-TPY = Ph-TPY, ClPh-TPY and MeOPh-TPY). The general formula and structural and supramolecular features were determinated by single-crystal X-ray diffraction for bis(4'-phenyl-2,2':6',2''-terpyridine)nickel(II) bis(perchlorate), [Ni(C21H15N3)2](ClO4)2 or [Ni(Ph-TPY)2](ClO4)2, bis[4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine]manganese(II) bis(perchlorate), [Mn(C22H17N3O)2](ClO4)2 or [Mn(MeOPh-TPY)2](ClO4)2, and bis(4'-phenyl-2,2':6',2''-terpyridine)manganese(II) bis(perchlorate), [Mn(C21H15N3)2](ClO4)2 or [Mn(Ph-TPY)2](ClO4)2. In all three cases, the complexes present distorted octahedral coordination polyhedra and the crystal packing is determined mainly by weak C-H...π interactions. All the compounds (except for the Ni derivatives, for which FT-IR, UV-Vis and thermal analysis are reported) were fully characterized by spectroscopic (FT-IR, UV-Vis and NMR spectroscopy) and thermal (TGA-DSC, thermogravimetric analysis-differential scanning calorimetry) methods.

Early bird or night owl? Controlling the ultrafast photodynamics of triphenylamine substituted 2,2':6',2''-terpyridine

Controlling the ultrafast photodynamics of metal-free organic molecules has great potential for technological applications. In this work, we use solvent polarity and viscosity as "external knobs" to govern the photodynamics of an electron-donating derivative of 2,2':6',2''-terpyridine (terpy), namely 4'-(4-(di(4-tert-butylphenyl)amine)phenyl)-2,2':6',2''-terpyridine (tBuTPAterpy). We combine femtosecond fluorescence upconversion (FlUC), transient absorption (TA) and quantum mechanical calculations to provide a comprehensive description of the tBuTPAterpy's photodynamics. Our results demonstrate that, by changing the solvent, the time scale of light-induced conformational changes of the system can be tuned over two orders of magnitude, controlling the tBuTPAterpy fluorescence spectral region and yield. As a result, depending on the local environment, tBuTPAterpy can act either as an "early bird" or a "night owl", with a tunability that makes it a promising candidate for metal-free sensors.

Role of the Environment Polarity on the Photophysical Properties of Mesogenic Hetero-Polymetallic Complexes

New hetero-polynuclear coordination complexes based on a pentacoordinated Zn(II) metal center with tridentate terpyridine-based ligands and monoanionic gallates functionalized with long alkyl chains containing ferrocene units were designed, synthesized and characterized using spectroscopic and analytical methods. The complexes are mesomorphic, exhibiting columnar hexagonal mesophases. The photophysical properties in a solution and in an ordered condensed state were accurately investigated and the influence of the polarity of the solvent was evidenced.

Fluorescent and chromogenic organic probes to detect group 10 metal ions: design strategies and sensing applications

Group 10 metals including Ni, Pd and Pt have been extensively applied in various essential aspects of human social life, material science, industrial manufactures, medicines and biology. The ionic forms of these metals are involved in several biologically important processes due to their strong binding capability towards different biomolecules. However, the mishandling or overuse of such metals has been linked to serious contamination of our ecological system, more specifically in soil and water bodies with acute consequences. Therefore, the detection of group 10 metal ions in biological as well as environmental samples is of huge significance from the human health point of view. Related to this, considerable efforts are underway to develop adequately efficient and facile methods to achieve their selective detection. Optical sensing of metal ions has gained increasing attention of researchers, particularly in the environmental and biological settings. Innovatively designed optical probes (fluorescent or colorimetric) are usually comprised of three basic components: an explicitly tailored receptor unit, a signalling unit and a clearly defined reporter unit. This review deals with the recent progress in the design and fabrication of fluorescent or colorimetric organic sensors for the detection of group 10 metal ions (Ni(II), Pd(II) and Pt(II)), with attention to the general aspects for design of such sensors.

Interfacial Self-Assembly of Organized Ultrathin Films of Tripodal Metal-Terpyridyl Coordination Polymers as Luminophores and Heterogeneous Catalysts for Photocatalytic CO2 Reduction

Metal-directed interfacial self-assembly of well-defined coordination polymer (CP) ultrathin films can control the metal complex arrangement and distribution at the molecular level, providing a convenient route for the design and fabrication of novel opto-electrical devices and heterogeneous catalysts. Here, we report the assembly of two series of CP multilayers with the transition-metal ions of Fe²⁺, Co²⁺, Zn²⁺ and Tb³⁺ as connectors and tripodal terpyridyl ligands of 4,4',4″-(1,3,5-triazine-2,4,6-triyl)tris(1-(4-([2,2':6',2″-terpyridin]-4'-yl)benzyl)pyridin-1-ium) (TerPyTa) and 4,4',4″-(benzene-1,3,5-triyl)tris(1-(4-([2,2':6',2″-terpyridin]-4'-yl)benzyl)pyridin-1-ium) (TerPyBen) as linkers at the air-water interface. The as-prepared Langmuir-Blodgett (LB) films display strong luminescence, with the emission wavelength and relative intensity dependent on both the metal ions and linkers; among them, the Zn-TerPyTa and Zn-TerPyBen CPs give off the strongest luminescent emission centered at about 370 nm with an emission lifetime of approximately 0.2-0.3 ns. The Tb-TerPyTa CPs can give off emission at approximately 490, 546, 586, and 622 nm, attributed to the ⁵D₄ to ⁷F_3-6 electron transitions of typical Tb³⁺ ions. Finally, these CP LB films can act as efficient heterogeneous photocatalysts for the CO₂ reduction to selectively produce CO. The catalytic efficiency can be optimized by adjusting the experimental conditions (light sensitizer, electron donor, and water content) and CP composition (metal ion and ligand) with an excellent yield of up to 248.1 mmol g^-1. In particular, it is revealed that, under the same conditions, the catalytic efficiency of the Fe-TerPyTa CP LB film is nearly 2 to 3 orders of magnitude higher than that of the other metalated complexes investigated in the homogeneous system. UV-vis spectroscopy and cyclic voltammetry studies demonstrated that the dual active sites of Fe-terpyridine and TerPyTa units contribute to the enhanced catalytic activity. This work provides an effective method to introduce the earth-abundant metal complexes into CP films to construct efficient noble-metal-free photocatalysts for the CO₂ reduction.

Substituents make a difference: 6,6″-modified terpyridine complexes with helix configuration and enhanced emission

A series of complexes L22-M (L2: 6,6″-bis(4-methoxyphenyl)-4'-phenyl-2,2':6',2″-terpyridine, M: Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) were synthesized by coordinating p-methoxyphenyl 6,6″-substituted terpyridine ligand with first-row transition metal ions and characterized by NMR, ESI-MS, and X-ray single crystal diffraction techniques. Single-crystal structures demonstrated that the steric hindrance of p-methoxyphenyl substituents endowed complexes L22-M with obvious longer coordination bond lengths and larger bond angles and dihedral angles compared with unmodified L12-M (L1: 4'-phenyl-2,2':6',2″-terpyridine). The chiral helix geometry was observed for L22-M, in which 2,2':6',2″-terpyridine moiety dramatically twisted to a spiral form in comparison to the nearly coplanar structure of the parent L12-M, resulting in plentiful intramolecular and intermolecular π-π interactions. Also, the appealing racemic (P and M) double helix packed structure for 6,6″-modified bisterpyridine complex L22-Cu was formed in the crystal. The consequent appealing charge transfer (CT) emission for L22-Zn in the solution and solid were investigated via UV-vis and fluorescence spectroscopy techniques and time-dependent density functional theory (TD-DFT) calculations. This work afforded a new method to achieve intriguing chiral geometry and CT optical properties via the subtle design and modification of terpyridine ligands.

Synthesis and Theoretical and Photophysical Study on a Series of Neutral Ruthenium(II) Complexes with Donor-Metal-Accepter Configuration

In order to construct a new type of ruthenium(II) terpyridine complexes with activated triplet metal-centered (³MC) states, as well as stabilized triplet metal-to-ligand charge transfer (³MLCT) states, conducive to fine emissive performances, Ru-1, Ru-2, Ru-3, and Ru-4 were synthesized. Compared with the [Ru(terpyridine)₂]²⁺ prototype (0.25 ns), this series of ruthenium(II) terpyridine complexes exhibit lengthened excited state lifetime (43.3 ns for Ru-1, 52.7 ns for Ru-2, 43.6 ns for Ru-3, and 53.4 ns for Ru-4). Interfragment charge transfer analysis illustrates the electron transfer direction of the four complexes, manifesting their intramolecular charge transfer characteristic. When excited, their lowest-lying triplet states are assigned as ³MLCT based on spin-density surface distribution. The singlet excited states and ³MLCT states were thoroughly studied by UV-visual absorption and nanosecond time-resolved transient absorption spectra, respectively. Photoluminescence spectra revealed their weak broadband near-infrared emission at room temperature and red phosphorescence at 77 K. The low molecular weight and the good thermal stability make Ru-1 and Ru-2 suitable for vaporization coating, while the fine solubility in common organic solvents makes Ru-3 and Ru-4 suitable for solution processing. Furthermore, the intrinsic electroneutrality and favorable energy levels endow them with new potential to be applied in the optoelectronic field.

Designing, Synthesis, and Anti-Breast Cancer Activity of a Series of New Quinazolin-4(1H)-one Derivatives

The inhibition of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) protein could be a promising treatment for breast cancer. In this regard, docking studies were accomplished on various functionalized organic molecules. Among them, several derivatives of quinazolin-4(1H)-one exhibited anti-breast cancer activity and satisfied the drug likeliness properties. Further, the in vitro inhibitory studies by a series of 2-(2-phenoxyquinolin-3-yl)-2,3-dihydroquinazolin-4(1H)-one molecules showed strong anti-cancer activity than the currently available drug, wortmannin. The MTT cytotoxicity assay was used to predict the anti-proliferative activity of these drugs against MCF-7 cancer cells by inhibiting the PIK3CA protein. The dose-dependent analysis showed a striking decrease in cancer cell viability at 24 h with inhibitory concentrations (IC₅₀ ) of 3b, 3c, 3d, 3f and 3m are 15±1, 17±1, 8±1, 10±1 and 60±1 (nanomoles), respectively. This is the first report in the literature on the inhibition of PIK3CA protein by quinazolinone derivatives that can be used in the treatment of cancer. Quinazolinone analogs have the potential to be safe and economically feasible scaffolds if they are produced using a chemical technique that is both straightforward and amenable to modification. From the cancer research perspective, this study can eventually offer better care for cancer patients.