Optical Sensor for Amine Vapors Based on Dimer−Monomer Equilibrium of Indium(III) Octaethylporphyrin in a Polymeric Film

Abstract

A novel transduction chemistry for the development of a polymer film-based optical sensor that responds reversibly to gas-phase amine species at sub-ppm levels is described. The sensor is based on the equilibrium of a indium(III) octaethylporphyrin hydroxide ion-bridged dimer species with corresponding monomeric porphyrins within a thin poly(vinyl chloride) film as a function of the level of volatile amine in the surrounding gas phase. The presence of amines causes the dimeric species to be converted to monomer via the ligation of the amine with the In(III) center of the porphyrin structure. This yields a significant change in the visible absorption spectrum of the film, with a decrease in the intensity of the Soret band corresponding to the dimer (lambdamax = 390 nm) and a concomitant increase in the Soret band for the monomer lambdamax = 406-408 nm). Response to different amines is based on their relative partition coefficient into the polymer film and their strength of axial ligation reactions, with a selectivity pattern of 1-butylamine > 1-propylamine > pyridine > triethylamine > ethylamine > methylamine > diethylamine > tert-butylamine > ammonia. It is further shown that a significant concentration of dimeric species within the polymer film can only be achieved if appropriate amounts of lipophilic anionic sites are also incorporated into the polymer in the form of a tetraphenylborate derivative and the resulting film is equilibrated briefly with water prior to gas-phase measurements. With optimized film compositions, 1-butylamine can be detected in the gas phase to levels approaching 0.1 ppm, while less lipophilic ammonia can be monitored down to 10 ppm, with fully reversible responses to each species. A simple mathematical model for the response of the amine sensor is presented and shown to predict the optical behavior observed.

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

“…Similar difficulties were observed previously with indium(III), gallium(III), and zirconium(IV) porphyrins as ionophores [9,12,34,35]. Recently, two strategies have been employed to eliminate dimer -monomer chemistry within the sensing membranes and improve overall electrode performance: (1) covalent attachment of the ionophore (In(III) porphyrin) to the polymer matrix [38], and (2) use of a porphyrin ligand with sufficient steric bulk (In(III)-or Ga(III)-picket fence porphyrin) [33].…”

“…It has been reported that other group 13 metalloporphyrins (Ga(III) and In(III)) form hydroxy-bridged dimer species [32], and that selective cleavage of these dimers by analyte ions (F À for Ga(III) and Cl À for In(III)) is responsible for the observed non-Nernstian behavior. [33] Indeed, such dimer - monomer chemistry has already been employed to construct optical sensors for chloride [34] and gaseous amines [35] since the dimeric and monomeric forms of the porphyrins exhibit significant differences in their l max for UV-Vis absorption. For the aluminum(III) porphyrin systems reported here, membrane electrodes equilibrated and conditioned with 10 mM fluoride (added to the internal solution, electrodes VIII and XII) display near-Nernstian fluoride response (see Fig.…”

Polymeric membrane electrodes with improved fluoride selectivity and lifetime based on Zr(IV)- and Al(III)-tetraphenylporphyrin derivatives

“…It is well known that most membrane electrodes based on metalloporhyrin ionophores have significant response to hydroxide ions [28,29]. Hydroxide has a great affinity to the metal ion center of examined metalloporphyrins (logK F-,OH-= 6.6, 6.9, 7.0 and 7.5 for electrodes 1, 9, 14 and 22 respectively) replacing the counterion of metalloporphyrin when in contact with water [30].…”

β-Cyclodextrin as a Metal-anionic Porphyrin Complexation Accelerator in Aqueous Media

“…[1][2][3][4][5][6][7][8][9] In addition, metal-porphyrin complexes have various functions that are useful in analytical chemistry, and are also of interest to many other researchers, which has led to the use of metal-porphyrin complexes in applications such as optics, 10 chemical stacking, 11 catalysis, 12 electron transport, 13 oxidation-reduction reactions, 14 and biological mimicking substances. 15,16 Thus, numerous reports regarding the chemical function and applications of porphyrin derivatives have been published.…”