We used the traditional hydro-thermal synthesis method to generate the first photochromic pyrimidinium/polyoxometalate (POM) salt material (C4N2H4–C4N2H3) Mn(H2O)60.5{SiW12O40}0.5ˑ5H2O in situ by ...using silicotungstic acid and pyrimidine as raw materials. The solid UV diffuse reflectance spectrum of compound 1 was shifted before and after illumination. There was a new broad absorption peak appeared near 370 nm and 624 nm after illumination. With the increase of irradiation time, the peak at 624 nm will shift to 588 nm at which the sample reached light saturation. The color of the sample changed from yellow to grayish green. By studying a series of test: EPR, XPS, UV–Vis, X-ray single crystal diffraction, and density of states (PDOS) calculation, we conclude that the charge transfer mechanism of photochromism may be due to: the generation of pyrimidinium free radicals by light-induced, photochemical reduction of polyoxometalates and the interaction of two aspects. This work enriches the family of photochromism and its theory.
Experiments for the first photochromic pyrimidinium/POM salt material (C4N2H4–C4N2H3)Mn(H2O)60.5{SiW12O40}0.5.5H2O and in-depth explored for the mechanism of photochromism. Display omitted
•The first photochromic pyrimidinium/polyoxometalate salt material.•Photochromic mechanism under the action of bifunctional groupsphotochromism.•Reversible photochromic materials at 370 nm, or between 657 nm and 588 nm.
Herein, we report an efficient synthesis of two novel probes for cyanide sensing based on 7-arylpyrazolo1,5-apyrimidinium salts PS (aryl = p-MeOPh) and T-PS (aryl = p-Ph2NPh). According to ...theoretical analyses, T-PS was found to be an ideal probe with improved absorption and emission properties due to a better intramolecular charge transfer (ICT) process. The experimental results, such as limit of detection (LOD; PS, 0.30 and 0.34 μmol/L → T-PS, 0.15, 0.15, and 0.25 μmol/L) and outstanding selectivity demonstrated the predicted properties. DFT calculations, HRMS analysis, and 1H NMR titration experiments were carried out to confirm the mechanism, regioselectivity, and reversibility of the CN– addition reaction in detecting the probes. These findings are especially attractive in the cyanide-sensing field. However, important repercussions on the sustainability performance, such as raw material costs and waste generation, were observed when comparing PS with T-PS. Satisfyingly, test strips fabricated using T-PS also demonstrated its practical applicability; in addition, emission in solid-state measurements of T-PS supported on silica showed its capability to detect cyanide ions in the solid state and in bitter almonds after 50 ppm. Ultimately, small amounts of CN– (0.5 μmol/L) in tap water detected by using the probe T-PS. Therefore, this work provides a sustainable and applicable approach in cyanide chemosensor preparation.
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels have a key role in the control of heart rate and neuronal excitability. Ivabradine is the first compound acting on HCN channels to ...be clinically approved for the treatment of angina pectoris. HCN channels may offer excellent opportunities for the development of novel anticonvulsant, anaesthetic and analgesic drugs. In support of this idea, some well-established drugs that act on the central nervous system - including lamotrigine, gabapentin and propofol - have been found to modulate HCN channel function. This Review gives an up-to-date summary of compounds acting on HCN channels, and discusses strategies to further explore the potential of these channels for therapeutic intervention.
Neuropathic pain is a common and often incapacitating clinical problem for which little useful therapy is presently available. Painful peripheral neuropathies can have many etiologies, among which ...are trauma, viral infections, exposure to radiation or chemotherapy, and metabolic or autoimmune diseases. Sufferers generally experience both pain at rest and exaggerated, painful sensitivity to light touch. Spontaneous firing of injured nerves is believed to play a critical role in the induction and maintenance of neuropathic pain syndromes. Using a well characterized nerve ligation model in the rat, we demonstrate that hyperpolarization-activated, cyclic nucleotide-modulated (HCN) "pacemaker" channels play a previously unrecognized role in both touch-related pain and spontaneous neuronal discharge originating in the damaged dorsal root ganglion. HCN channels, particularly HCN1, are abundantly expressed in rat primary afferent somata. Nerve injury markedly increases pacemaker currents in large-diameter dorsal root ganglion neurons and results in pacemaker-driven spontaneous action potentials in the ligated nerve. Pharmacological blockade of HCN activity using the specific inhibitor ZD7288 reverses abnormal hypersensitivity to light touch and decreases the firing frequency of ectopic discharges originating in Abeta and Adelta fibers by 90 and 40%, respectively, without conduction blockade. These findings suggest novel insights into the molecular basis of pain and the possibility of new, specific, effective pharmacological therapies.
Betaine derivatives are widely used in cosmetic, industrial uses, biology and other scientific fields. Pyrimidinium betaine is a special class of bioactive heterocyclics. They have interesting ...antioxidant and free radical scavenging activities. This work aims to examine the influence of some parameters on the antioxidant activity of some synthesized betaines containing pyrimidine ring. Four pyrimidinium betaines: monocyclic, bicyclics, and one with a fatty alkyl chain were synthesized from condensation of 2-aminopyrimidine or amidine derivatives with malonic esters, and their antioxidant capacity was evaluated. The effects of concentration, reaction time and temperature on their antioxidant activities were investigated by three common methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferric reducing antioxidant power (FRAP) and β-carotene bleaching. The results showed that all pyrimidinium betaines exhibited antioxidant activities in different assays. In the DPPH and reducing power assays, antioxidant activity increased with concentration, whereas in the β-carotene/linoleic acid system, it increased with temperature. On the other hand, the DPPH assay showed an increase in antioxidant capacity over time, while the β-carotene bleaching assay showed a decrease. These results indicate that the antioxidant activity differs depending on the method used and that the various factors affect the antioxidant activity in a different order.
A novel n-type cationic conjugated polymer (PFSOmiCl), consisting of bispyrimidinium-dibenzothiophene-S,S-dioxide and fluorene scaffolds, was developed from its polymeric precursor (PFSOmi) through ...an intramolecular cyclization reaction. In comparison with PFSOmi, PFSOmiCl exhibits significant bathochromical absorption and photoluminescence spectra in both solution and film form, as well as a more hydrophilic film surface. Cyclic voltammetry tests demonstrate that PFSOmiCl possesses a deep lowest unoccupied molecular orbital (LUMO) energy level of −4.18 eV, which is comparable to the LUMO energy levels of common fullerene derivatives. These unique properties endow PFSOmiCl with great utilization potential in organic optoelectronic devices. Moreover, this research offers a novel guideline for designing new conjugated polyelectrolytes.
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The proton‐transfer complexes 2‐amino‐4‐methoxy‐6‐methylpyrimidinium (2A4M6MP) 4‐aminosalicylate (4AMSA), C6H10N3O+·C7H6NO3−, I, and 5‐chlorosalicylate (5ClSA), C6H10N3O+·C7H4ClO3−, II, were ...synthesized by slow evaporation and crystallized. The crystal structures of both I and II were determined by single‐crystal X‐ray structure analysis. The crystal structures of both salts exhibit O—H…O, N—H…O, N—H…N and C—H…O interactions in their crystals. The 4AMSA and 5ClSA anions in combination with the 2A4M6MP cations form distinct synthons, which are represented by the graph‐set notations R22(8), R42(8) and R22(8). Furthermore, the ΔpKa values were calculated and clearly demonstrate that 2A4M6MP is a good salt former when combined with carboxylic acids. Hirshfeld surface analysis was used to quantify the weak and strong interactions in the solid state, and energy framework calculations showed the stability of the hydrogen‐bonding interactions. QTAIM (quantum theory of atoms in molecules) analysis revealed the nature of the chemical bonding in I and II, and the charge–density distribution in the intermolecular interactions in the crystal structures.
The proton‐transfer complexes of 2‐amino‐4‐methoxy‐6‐methylpyrimidinium with 4‐aminosalicylate and 5‐chlorosalicylate were synthesized by slow evaporation and crystallized. The cations and anions form distinct synthons. Energy framework calculations showed the stability of the hydrogen‐bonding interactions. QTAIM analysis revealed the nature of the chemical bonding and the charge–density distribution in the intermolecular interactions in the crystal structures.
The title compound, C
D
ClN
O
·Cl
, crystallizes in the ortho-rhom-bic space group,
, and consists of a 4-chloro-2-methyl-6-oxo-3,6-di-hydro-pyrimidin-1-ium cation and a chloride anion where both ...moieties lie on a crystallographic mirror. The cation is disordered and was refined as two equivalent forms with occupancies of 0.750 (4)/0.250 (4), while the chloride anion is triply disordered with occupancies of 0.774 (12), 0.12 (2), and 0.11 (2). Unusually, the bond angles around the C=O unit range from 127.2 (6) to 115.2 (3)° and similar angles have been found in other structures containing a 6-oxo-3,6-di-hydro-pyrimidin-1-ium cation, including the monclinic polymorph of the title compound, which crystallizes in the monoclinic space group
2
/
Kawai
(1973 ▸).
, 663-666. The cations and anions pack into sheets in the
plane linked by N-H⋯Cl hydrogen bonds as well as C-H⋯O and Cl⋯O inter-actions. In graph-set notation, these form
(11) and
(9) rings. Theoretical calculations seem to indicate that the reason for the unusual angles at the
C is the electrostatic inter-action between the oxygen atom and the adjacent N-H hydrogen.
Pyrido1,2-apyrimidinium salt derivatives 2a-f were prepared in good yields by condensation of 2-aminopyridine with 2-substituted vinamidinium salt derivatives 1a-f. The purity and the structure of ...the synthetized compounds were ascertained by elemental analysis, mass spectrometry, infrared, and NMR (¹H and ¹³C 400 MHz) spectroscopy.
Although conduction failure has been observed in nociceptive C-fibers, little is known regarding its significance or therapeutic potential. In a previous study, we demonstrated that C-fiber ...conduction failure, which is regarded as an intrinsic self-inhibition mechanism, was reduced in circumstances of painful diabetic neuropathy. In this study, we extend this finding in the complete Freund's adjuvant model of inflammatory pain and validate that the degree of conduction failure decreased and led to a greater amount of pain signals conveyed to the central nervous system. In complete Freund's adjuvant-injected animals, conduction failure occurred in a C-fiber-selective, activity-dependent manner and was associated with an increase in the rising slope of the C-fiber after-hyperpolarization potential. To target conduction failure in a therapeutic modality, we used ZD7288, an antagonist of hyperpolarization-activated, cyclic nucleotide-modulated channels which are activated by hyperpolarization and play a pivotal role in both inflammatory and neuropathic pain. ZD7288 promoted conduction failure by suppressing Ih as a mechanism to reduce the rising slope of the after-hyperpolarization potential. Moreover, perineuronal injection of ZD7288 inhibited abnormal mechanical allodynia and thermal hyperalgesia without affecting motor function or heart rate. Our data highlight the analgesic potential of local ZD7288 application and identify conduction failure as a novel target for analgesic therapeutic development.
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