Synthesis and characterization of two cyanoxime ligands, their precursors, and light insensitive antimicrobial silver(I) cyanoximates

Abstract

High-yield syntheses of N-piperidine-cyanacetamide (1), N-morpholyl-cyanacetamide (4) and their oxime derivatives N-piperidine-2-cyano-2-oximino-acetamide (HPiPCO, 2) and N-morpholyc-2-cyano-2-oximino-acetamide (HMCO, 5) were developed using two-step preparations. At first, the reactions of neat cyanoacetic acid esters and the respective cyclic secondary amines such as piperideine and morpholine afforded pure cyanacetamides, which were converted into cyanoximes at room temperature using the nitrosation reaction with gaseous CH3ONO. The synthesized compounds were investigated by means of IR, 1H, 13C and UV-visible spectroscopy. Crystal structures of two starting substituted cyan-acetamides and two target cyanoximes were determined. Silver(I) complexes of AgL composition (L = PipCO, 3; MCO, 6) were prepared in high yield. Both metal complexes are thermally stable above 100oC, and remarkably stable to high intensity visible light. The stability of dried AgL compounds towards short wavelength UV-radiation (a frequently used germicidal light) was examined using diffusion reflectance spectroscopy. Both complexes demonstrate slow photoreduction within ~3 hrs, observable as a gradual color change and darkening due to the formation of fine (nano-scale) particles of metallic silver. The complex Ag(MCO), 6, is about 2.6 times less stable towards UV-radiation than its more lypophyllic analog Ag(PipCO), 3. Antimicrobial and biofilm growth inhibition properties of the prepared solid acrylate-based polymeric composites containing embedded silver(I) cyanoximates were investigated using three human pathogens: P. aeruginosa PAO1 (wound isolate), S. aureus NRS70 (methicillin resistant respiratory isolate), and S. mutans UA159 (cariogenic dental isolate). Studies showed that both 3 and 6 compounds completely abolished the growth of PAO1 at 0.5 weight % concentration, and the growth of UA159 and NRS70 at 1% concentration. Moreover, data demonstrates that complexes 3 and 6 also inhibit both planktonic and biofilm growth of Gram-positive and Gram-negative bacterial pathogens. The demonstrated thermal stability and pronounced antimicrobial activity of both silver(I) cyanoximates indicates the strong potential for the studied complexes to be used as light insensitive antimicrobial additives to light-curable adhesives that set indwelling devices in place.

Shortwave infrared luminescent Pt-nanowires: a mechanistic study of emission in solution and in the solid state

“…36, 63 These compounds were found to have two polymorphs: the HMCO crystallizes in two different orthorhombic polymorphs in a P2 1 2 1 2 1 space group, while HPiPCO can crystallize in either monoclinic 63 P2 1 /c, or orthorhombic 36 P2 1 2 1 2 1 space groups. The crystal structures of three Pt-cyanoximates were determined using the X-ray crystallography and the structure of one 1D-polymeric complex was elucidated by the EXAFS method.…”

1D Polymeric Platinum Cyanoximate: A Strategy toward Luminescence in the Near-Infrared Region beyond 1000 nm

“…We also rationalized that the anion’s bulkiness from substituents would control the distance between the metal centers. Therefore, among known cyanoxime ligands, those with amide groups provide a greater variety of electronic and steric properties and solubility. − Thus, novel bivalent palladium and platinum complexes were synthesized using a cyanoxime ligand well soluble in organic solvents, 2-cyano-2-oximino- N , N ′-diethylaminoacetamide [HDECO, 1 ]. As we demonstrate below, the platinum complex self-assembles in solutions into a luminescent 1D polymeric “poker-chips” structure.…”

Polymeric Composites with Silver (I) Cyanoximates Inhibit Biofilm Formation of Gram-Positive and Gram-Negative Bacteria

“…Variability in the antimicrobial activity of silver compounds was anticipated based on our earlier report for Ag(MCO) and Ag(PiPCO) [45], as well as previously reported strain specificity of the antimicrobial effect of silver nanoparticles (AgNPs) [60]. The latter were tested against four strains of Gram-negative Escherichia coli and Gram-positive two strains of B. subtilis and three strains of S. aureus .…”

“…We initiated synthesis and characterization of structures and properties of the new family of silver cyanoximates (reviewed in Reference [42]) and performed a preliminary assessment of their antimicrobial activity [43], followed by their further detailed characterization [44]. In the most recent work, we obtained two previously unknown AgL (L = 2-oximino-2-cyano-N-morpholylacetamide, MCO- and 2-oximino-2cyano-N-piperidineacetamide, PiPCO-), which were added to the list of visible light and heat stable, poorly water soluble antimicrobial compounds [45]. Also, we pioneered the addition of solid powders of Ag(MCO) and Ag(PiPCO) into the light-curable acrylate-based polymeric composite, widely used in medical practice [45].…”

“…In the most recent work, we obtained two previously unknown AgL (L = 2-oximino-2-cyano-N-morpholylacetamide, MCO- and 2-oximino-2cyano-N-piperidineacetamide, PiPCO-), which were added to the list of visible light and heat stable, poorly water soluble antimicrobial compounds [45]. Also, we pioneered the addition of solid powders of Ag(MCO) and Ag(PiPCO) into the light-curable acrylate-based polymeric composite, widely used in medical practice [45]. This enables applications of these compounds as antimicrobial additives to adhesives and fillers for indwelling medical devices.…”