Stable citrate-capped silver nanoparticles (AgNPs) were developed as a colorimetric sensing probe for selective detection of ampicillin in urine samples.

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Calixarenes with their three dimensional structural architecture and suitable functionalization at upper and/or lower rim are well-known for their plethora of application in chemical, physical, biological and other deciplines. Herein,...

Three 25,26-bridged para-tert-butyl-calix [4]arene phosphites, 1-3, have been synthesized by linking two proximal phenolic oxygen atoms of para-tert-butyl-calix [4]arene to a P(OR) [R = 2,6-Bu t 2 -4-Me-C 6 H 2 (1), 2,6-Pr i 2 -C 6 H 3 (2) or 2,4-Bu t 2 -C 6 H 3 (3)] moiety. NMR spectroscopic data and X-ray crystallographic studies (1 and 2 only) show that the calixarene framework in 1 adopts a cone conformation, whereas in 2 and 3 it assumes a partial cone conformation. Unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites 5-7 have been synthesized by the reaction of 25,26-bridged para-tert-butyl-calix[4]arene phosphite 1 with (R 0 O)PCl 2 [R 0 = 2,4-Bu t 2 -C 6 H 3 (5), 2,6-Pr i 2 -C 6 H 3 ( 6) or (1R,2S,5R)-(À)menthyl ( 7)]. NMR investigations (homonuclear 31 P COSY) revealed an unprecedented ''through-space'' phosphorus-phosphorus coupling of 223-244 Hz for these unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites. The molecular structure of unsymmetrical 25,26;27,28-bridged bisphosphite 5 was determined by X-ray crystallography; the two phosphorus atoms are in close proximity and the PÁ Á ÁP distance (3.543(2) A ˚) is less than the sum of their van der Walls radii.