Influence of substituent and ligand electronic factors on the measurement of gas phase olefins using a surface acoustic wave oscillator coated with trans-PtCl2(olefin)(amine) complexes

Abstract

Certain olefin gases and vapors can be measured selectively at low concentrations using surface acoustic wave (SAW) sensors vated with reagents of the general formula trans-PtClz(olefin)(amine). The sensor response depends on the steady-state rate of mass change associated with substitution of the initially complexed olefin by the free olefin analyte. This paper examines the effects of changes in the electronic nature of substituents on the free olefin and the olefin and amine ligands in the complex on the sensitivity and selectivity obtained with this class of SAW sensor coatings. For a given reagent, higher reaction rates are generally observed with electron-donating substituents on the double bond of the free olefin. For a given free olefin, varying the 4-substituent of the pyridine ligand in PtCl,(ethyleneX4-X-pyridine)gives a maximum response at an intermediate degree of amine basicity. Replacing pyridine by aniline, pyridine N-oxide or the 4-substituted derivatives of these ligands results in reduced responses for the olefins tested. Changing the initially complexed olefin leads to large changes in response, the pattern of which varies with the nature of the free olefin. Results demonstrate the potential for controlling the response of SAW sensors through subtle structural modifications of these coating reagents.

Acoustic Wave Microsensor Arrays for Vapor Sensing

“…Reactive layers for acoustic wave sensors have been described by Zellers et al − A variety of metal complexes were investigated for their ability to selectively react with and retain olefin vapors. Though not reversible, they can be regenerated.…”

Acoustic Wave Sensors

“…It is also possible to create selective layers that react chemically with vapors to give irreversible responses. This approach has been explored in detail for a variety of olefincontaining vapors [180][181][182][183][184].…”

Exploiting Charge-Transfer Complexation for Selective Measurement of Gas-Phase Olefins with Nanoparticle-Coated Chemiresistors

“…For applications where a specific vapor or class of vapors is targeted, additional selectivity is often desirable to eliminate or reduce the influence of coeluting interferences. An example of this is found in some earlier work from our group in which charge-transfer complexes of the general formula PtCl 2 (olefin)(pyridine) were used as components of interface layers on surface acoustic wave (SAW) sensors to achieve unique selectivity for certain olefin gases and vapors. − Olefin substitution in such complexes proceeds via a bimolecular pentacoordinate intermediate. − Dissociation of the original olefin yields a stable Pt complex that readopts the initial square-planar geometry with the new olefin coordinated (see Scheme ). With PtCl 2 (ethylene)(pyridine) the substitution proceeds readily at room temperature, and non-olefins neither react with the Pt−olefin complex nor interfere with the reaction with the target olefins. − The high degree of selectivity obtainable with such a sensor interface is traded off against the finite amount of reagent that can be accommodated on the surface of a microsensor, which limits the useful lifetime of the sensor.…”

“…An example of this is found in some earlier work from our group in which chargetransfer complexes of the general formula PtCl 2 (olefin)(pyridine) were used as components of interface layers on surface acoustic wave (SAW) sensors to achieve unique selectivity for certain olefin gases and vapors. [28][29][30][31][32][33] Olefin substitution in such complexes proceeds via a bimolecular pentacoordinate intermediate. [34][35][36][37][38][39][40][41] Dissociation of the original olefin yields a stable Pt complex that readopts the initial square-planar geometry with the new olefin coordinated (see Scheme 1).…”