A cyclometalated N-heterocyclic carbene and acetylacetonate ligands in a phosphorescent Pt(II) dye for sensing glucose

New beta-diketonate platinum (II) complexes, containing a cyclometalated N-heterocyclic carbene [Pt(Naph boolean AND C*(iPr)) (acac)] (3A) (HNaph boolean AND C*-kappa C* = 3-isopropyl-1-(naphthalen-2-yl)-1H-imidazole-2-ylidene), or a cyclometalated pyrazole, [Pt(Naph boolean AND N-pz)(acac)] (3B) (HC boolean AND N-pz = 1-(naphthalen-2-yl)-1H-pyrazole) and [Pt(Naph boolean AND N-dmpz)(acac)] (3B') (HC boolean AND N-dmpz = 1-(naphthalen-2-yl)-1H-3,5-dimethylpyrazole) have been prepared and characterized. Their absorption and emission properties in films of ethyl cellulose (EC) were determined along with those of the already reported for complex [Pt(Naph boolean AND C*(Me))(acac)] (3A'). They showed that all four beta-diketonate complexes display a bright phosphorescent emission with maxima in the blue region (lambda(max) similar to 480 nm for 3A and 3A'; 490 nm 3B and 3B'). The higher quantum yield (QY), longer decay times and greater oxygen sensitivity were exhibited by the Naph boolean AND C* derivatives, compared to the Naph boolean AND N ones. Polyacrylamide membranes with entrapped 3A' as dye, and glucose oxidase (GOx) enzyme were used for monitoring glucose level. The RSD is about 5% and the detection limit is at similar to 5.10(-4) M, with a response time usually of 10-15 min working in stop-flow mode. These platinum-based membranes respond reversibly to glucose for, at least, 20 measures. 3A' is the first Pt(II) complex bearing a cyclometalated N-heterocyclic carbene ever used as dye for sensing glucose.