Tricarbonyl(cyclohexadiene)iron(0) reporting groups have been derivatized by attachment of an aminopropylsilyl link and attached covalently to silica. The IR properties of the organometalearbonyl moiety have been investigated by Fourier Transform infrared spectroscopy and have been shown to retain their capacity to function as a key element of a molecular sensor assembly. The v(CO) vibrational frequencies of the immobilised complexes shift with changes in the solvent environment when exposed to binary and ternary solvent systems. Principal components regression (PCR) was used to correlate the v(CO) shifts of the probe group quantitatively with solvent composition with a RMSEP error of 0.9% for a binary solvent system. Tricarbonyl(η⁵-cyclohexadienyl)iron(O) and dicarbonyl(triphenylphosphine)(η⁵-cyclohexadienyl)iron(0) have been derivatized by attachment of an aminopropylsilyl link and covalently attached to fumed silica particles. The fumed silica was coated onto the ZnSe element of an ATR cell for Fourier Transform infrared (FTIR) spectroscopic analysis. The immobilized organometalearbonyl probe groups are shovm to retain their capacity to function as a key element of a molecular sensor assembly and the v(CO) bands of the two probe groups have been interrogated to calibrate the responses for 0-5% levels of dodecane in cyclohexanol to within ± 0.1%. The potential of dual sensing is described and the simultaneous monitoring of two discrete regions of a dynamically varying inhomogeneous system is reported for the determination of dodecane in cyclohexanol as solutions mix across a permeable barrier in the ATR cell. A fibre optic ATR probe has been used to monitor reactions between organometallie complexes in controlled environments. This probe has been used to construct an optrode sensor by coatmg fumed silica particles incorporating covalently attached organoironcarbonyl probe groups onto the ZnSe attenuated total reflectance element tip. The sensor may be interrogated remotely using FTIR spectroscopy by coupling IR transparent optical fibres to the ATR element. The organometallie probe groups act as components of a sensing system in which analyte/sensor interactions are transduced through shifts in the sharp v(CO) bands of the metal carbonyl reporting group. The potential of the device is demonstrated for pH sensing in the range 7-13 and as a sensor of solvent environment. Coating two different immobilized probe groups onto the ATR element, combined with FTIR measurement, allows the optrode to be used for the independent, multi-component sensing of two analytes.