Carboxylate complexes have risen to prominence in the field of water oxidation catalysis. Here for the first time we use the higher valence of phosphinates [P(V)] relative to that of carboxylates [C(IV)] to increase ligand denticity. We describe the synthesis and characterization of a new dianionic pentadentate ligand, bcpq2- that contains a tridentate 2,2’-bipyridine-6-carboxylato moiety, in addition to a 6’-phosphinato substituent that acts as fourth ligand and bears a side arm containing a quinoline, the fifth ligand. The new bcpq ligand allows formation of [Ru(II)(bcpq)(L)] (2a-b, L = picoline or isoquinoline) and in preliminary results, of a Co(II) complex. NMR spectroscopy, X-ray diffraction, cyclic voltammetry, differential pulse and square wave voltammetry were used to characterize 2a-b, with 2b being characterized more extensively as a catalyst. Bulk electrolysis over 15 h at pH 7 was also used, showing that 2b gave 100 ± 5 % faradaic efficiency and remained completely homogeneous, whereas 1b was no longer homogeneous; this comparison conclusively shows the advantage of the added denticity in the electrocatalytic context. Replacing carboxylate with P(V) phosphinate with an added arm may be used in other ligand systems to enhance the durability of homogeneous catalysts.
Azomethine Fe3+ coordination compounds containing carbazole units: Synthetic approach, spectral characterization, and magnetic studies
The main aim of our study is to investigate various types of hybrid systems with a paramagnetic iron (III) ion as a core and photoactive derivatives of carbazole at the periphery. We have synthesized a variety of biligand coordination compounds with the composition [FeL 2 ]A (where L is 2-[2-[(E)-[4-[4-(3,6-di-tert-butylcarbazol-9-yl)benzoyl]oxy-2-phenolate]methyleneamino]ethylamino]ethyl 4-(3,6-di-tert-butylcarbazol-9-yl)benzoate and A− is NO3 − (I), Cl− (II), PF6 − (III)). These systems were studied by SQUID magnetometry and X-band EPR spectroscopy. Magnetic measurements revealed mixed spin states (HS, LS) of the Fe (III) ions at room temperatures. The estimations of the corresponding spin contributions were made. It was found that all compounds demonstrate AFM exchange interactions between the Fe (III) ions. Ground spin states at 2.0 K were established and analyzed. EPR measurements confirmed Fe (III) HS states and reveal two types of them: with weak distorted and strong low-symmetry octahedral crystal fields.
The main aim of our study is to investigate various types of hybrid systems with a paramagnetic iron (III) ion as a core and photoactive derivatives of carbazole at the periphery. We have synthesized a variety of biligand coordination compounds with the composition [FeL 2 ]A (where L is 2-[2-[(E)-[4-[4-(3,6-di-tert-butylcarbazol-9-yl)benzoyl]oxy-2-phenolate]methyleneamino]ethylamino]ethyl 4-(3,6-di-tert-butylcarbazol-9-yl)benzoate, A− is NO3 − (I), Cl− (II), PF6 − (III)). These systems were studied by superconducting quantum interference device (SQUID) magnetometry and X-band electron paramagnetic resonance (EPR) spectroscopy. Magnetic measurements revealed mixed spin states (high spin [HS], low spin [LS]) of Fe (III) ions at room temperatures. Estimates of the corresponding spin contributions were made. It was found that all samples exhibit AFM exchange interactions between iron (III) ions. The ground spin state at 2.0 K was established and analyzed. EPR measurements confirmed the HS states of iron (III) and revealed two types of them: with weak distorted and strong low-symmetry octahedral crystal fields.
Nonperipherally and peripherally substituted water‐soluble magnesium (II) phthalocyanines and their DNA binding, nuclease activities
We have synthesized magnesium (II) phthalocyanines (2a, 3a) and their water-soluble derivatives (2b, 3b). The ct-DNA binding and supercoiled plasmid DNA nuclease properties of the water-soluble compounds were investigated using different methods. All of these results showed that 2b had promising potential as a photosensitizer agent for photodynamic therapy.
In this study, magnesium (II) phthalocyanines (2a, 3a) and their water-soluble derivatives (2b, 3b) were synthesized via multistep reactions. The structures of these phthalocyanines were identified by FT-IR, NMR, MALDI-TOF, and UV–Vis spectroscopy. The ct-DNA binding (UV–Vis absorption, competitive EB binding, and agarose electrophoresis studies) and supercoiled plasmid DNA nuclease properties (hydrolytic, photonuclease, oxidative nuclease, and photooxidative nuclease) of the water-soluble compounds were investigated using different methods. The DNA binding constant (K b ) values of 2b and 3b were calculated as 8.45 ± (0.25) × 104 and 7.71 ± (0.13) × 104 M−1 at 25°C, respectively. The results showed that 2b had a stronger ct-DNA binding effect than 3b according to K b and r values. The DNA nuclease studies claimed that both compounds indicated photonuclease activity on plasmid DNA depending on the light dose. Additionally, 2b had a higher photonuclease capacity than 3b. All of these results showed that 2b had promising potential as a photosensitizer agent for photodynamic therapy.
Water‐Doped Brønsted Acidic Protic Ionic Liquids for Enhanced Tributyl Citrate Synthesis in a Two‐Phase Esterification System
Tributyl citrate (TBC) plays a crucial role as a plasticizer, enhancing the flexibility of polymers like polyvinyl chloride. Its biodegradability and non-toxic nature contribute to its eco-friendly appeal, making it a preferred additive in diverse industries, including food packaging, medical devices, toys, and consumer goods. Herein, a method for the synthesis of TBC using inexpensive Brønsted acidic protic ionic liquids (ILs) in a two-phase reaction system is presented. The esterification process is carried out with high yield (>99%), selectivity (up to 98%) and short reaction time of 2h. The catalyst in the form of IL shows excellent performance and stability, desirable for industrial applications.
Bifunctional Sildenafil Diazeniumdiolates Acting as Phosphodiesterase 5 Inhibitors and Nitric Oxide Donors ̶ Towards Wound Healing
Inefficient wound healing poses a global health challenge with a lack of efficient treatments. Wound healing issues often correlate with low endogenous nitric oxide (NO) levels. While exogenous delivery with NO-releasing compounds represents a promising therapeutic strategy, controlling the release of the highly reactive NO remains challenging. Phosphodiesterase 5 (PDE5) inhibitors, like sildenafil, have also been shown to promote wound healing. This study explores hybrid compounds, combining NO-releasing diazeniumdiolates with a sildenafil-derived PDE5 inhibitor. One compound demonstrated a favorable NO-release profile, triggered by an esterase (prodrug), and displayed in vitro nanomolar inhibition potency against PDE5 and thrombin-induced platelet aggregation. Both factors are known to promote blood flow and oxygenation. Thus, our findings unveil promising prospects for effective wound healing treatments.
Unraveling Ferroptosis Mechanisms: Tracking Cellular Viscosity with Small Molecular Fluorescent Probes
Ferroptosis is a recently identified form of regulated cell death characterized by iron accumulation and lipid peroxidation. Numerous functions for ferroptosis have been identified in physiological as well as pathological processes, most notably in the treatment of cancer. The intricate balance of redox homeostasis is profoundly altered during ferroptosis, leading to alteration in cellular microenvironment. One such microenvironment is viscosity among others such as pH, polarity, and temperature. Therefore, understanding the dynamics of ferroptosis associated viscosity levels within organelles is crucial. To date, there are a very few reviews that detects ferroptosis assessing reactive species. In this review, we have summarized organelle’s specific fluorescent probes that detects dynamics of microviscosity during ferroptosis. Also, we offer the readers an insight of their design strategy, photophysics and associated bioimaging concluding with the future perspective and challenges in the related field.
Hollow nitrogen‐doped carbon spheres as zincophilic sites for Zn flow battery
Severe dendrite growth on Zn anodes poses a significant challenge to the development of Zn-based batteries. An effective strategy for inhibiting the formation of Zn dendrites involves electrode modification. In this study, hollow nitrogen-doped carbon spheres (HNCS) are synthesized and used as electrodes to regulate Zn deposition in Zn-based flow batteries. The electrochemical performance of HNCS reveals that the pyrrole nitrogen of HNCS changes the electrode surface state. Therefore, HNCS can inhibit the hydrogen evolution reaction and achieve uniform Zn deposition. HNCS can effectively inhibit dendrite growth and improve the reversibility of the Zn plating/stripping process to regulate the reversibility of Zn-based batteries. The zinc–bromine redox flow battery assembled with HNCS significantly reduces the hydrogen evolution reaction and exhibits a coulombic efficiency of 90% and energy efficiency of 73% at a current density of 60 mA cm–2. Similarly, an alkaline zinc–iron flow battery can maintain high Coulombic efficiency and energy efficiency of 83%.
Photoinduced [2+2] and [4+4] Cycloaddition and Cycloreversion Reactions for the Development of Photocontrollable DNA Binders
![Photoinduced [2+2] and [4+4] Cycloaddition and Cycloreversion Reactions for the Development of Photocontrollable DNA Binders](https://chemistry-europe.onlinelibrary.wiley.com/cms/asset/01d4efad-88fb-431c-9698-6d6e450171f8/cptc202300318-toc-0001-m.png)
In this Concept Article the scope, the limits, and the potential of the photoinduced [2+2] and [4+4] cycloaddition–cycloreversion sequence in the development of photoswitchable DNA binders are presented.
Abstract
In the current field of photopharmacology, molecular photoswitches are applied whose interactions with DNA can be triggered or controlled by light. And although several photochromic reactions have been shown to serve this purpose well, the reversible photocycloaddition and photocycloreversion reactions have been largely neglected. This absence of research is surprising because especially the photodimerization of a DNA ligand leads to products with significant change of the size and shape which, in turn, leads to strongly diminished or even suppressed DNA association. Therefore, photocycloaddition–cycloreversion sequences have a huge potential for the photoinduced, reversible deactivation and activation of ligand–DNA interactions, as will be shown with selected examples in this Concept Article. Specifically, heterostyryl and -stilbene derivatives are presented whose DNA–binding properties are efficiently switched in reversible [2+2] photocycloaddition reactions. In addition, the photocontrolled DNA–binding of anthracene derivatives and their heterocyclic benzo[b]quinolizinium analogues in a [4+4] photocycloaddition, as well as the use of this reaction as part of dual–mode switches in combination with redox-active functionalities, are highlighted. Furthermore, examples of conjugates are provided, in which the photochromic unit is bound covalently to nucleic acids or proteins, such that the photocycloaddition reaction can be used for reversible photoinduced crosslinking, ligation, or inhibition of gene expression.
Triplet Excited State Mechanistic Study of meso‐Substituted Methylthio Bodipy Derivative: Time‐Resolved Optical and Electron Paramagnetic Resonance Spectral Studies
Understanding the intersystem crossing (ISC) mechanism of organic compounds is essential for designing new triplet photosensitizers. We investigated the ISC mechanism of a heavy atom-free Bodipy derivative with thiomethyl substitution (S-BDP). A long-lived triplet state was observed with nanosecond transient absorption spectroscopy with lifetime of 7.5 ms in a polymer film and 178 ms in fluid solution, longer as compared with what was previously reported . Femtosecond transient absorption studies retrieved an ISC time constant of ~3 ns. Time-resolved electron paramagnetic resonance (TREPR) indicated a special triplet electron spin polarization phase (ESP) pattern (a, e, a, e, a, e), different from the typical ESP (e, e, e, a, a, a) for the spin-orbit coupling mechanism. This indicates that the electron spin selectivity of the ISC of S-BDP is different from the normal SOC effect in iodo-Bodipy. Simulations of the TREPR spectra give a zero-field-splitting D parameter of -2257 MHz, much smaller as compared to the reference 2,6-diiodo-Bodipy (D = -4380 MHz). The computed SOC matrix elements (0.28-1.59 cm-1) and energy gaps for the S1/Tn states suggest that the energy matching between the S1 and T2/T3 states (supported by the largest kISC ~109 s-1) enhances the ISC for this compound.
Multifunctional Logic Operations Based Upon Congruent ion Sensing Appended with a Strategic Molecular Device: Spectroscopic Approach
A multi-responsive smart molecular system was constructed on a newly synthesized Salen molecule, 1,3-bis((E)-2,3,4-trimethoxy benzylideneamino) propan-2-ol (TMBP) to selectively validate the presence as well as the absence of Cu2+ dictated by another selective metal ion, Zn2+. The emission efficiency of the non-emissive probe was significantly enhanced by Zn2+ selectively, while specific binding of the probe-Zn2+ complex with Cu2+ completely quenched the enhanced emission. Thus, the probe acted as a reporter molecule for the selective detection of Cu2+ in the co-presence of Zn2+. Comprehensive spectroscopic studies indicated that Zn2+ ion-coordination significantly reduced the flexibility of the Schiff base unit and decreased the extent of photoinduced electron transfer (PET) enabling an enhancement of fluorescence intensity. While, Cu2+, a d9 system, induced paramagnetic quenching through formation of a stable ground-state complex as established from the UV-Vis analysis and time resolved fluorescence measurements. The spectroscopic results were implemented into the designing of a multifunctional molecular logic system that could function as YES, NOT, INHIBIT, PASS 0, TRANSFER and NOT TRANSFER logic gates. Finally, a blueprint of a smart molecular device was proposed to present the relay sensing of Zn2+ and Cu2+ through logical outputs that would work in-sync with the spectroscopic results.