Control of detection limits in pulsed-accelerated-flow spectrophotometry and rates of inner-sphere electron transfer and axial water exchange in nickel(III) tripeptides, tripeptideamides, and macrocycles
Abstract
Statistical process control techniques are used to determine and monitor the detection limit for pulsed-accelerated-flow (PAF) spectrophotometry. Control charts for individual background measurements and for moving ranges of individual background measurements provide decision rules for determining the smallest measurable absorbance change with 95% confidence. Probabilities are tabulated for controlling the background component of the measurement as a function of ensemble size. Rate constants for inner-sphere electron transfer are measured for Ni(III) tripeptides, tripeptideamides, and macrocycles with cyanide containing reductants. An inner-sphere mechanism is given which accounts for kinetic advantage values ranging from 10$\sp2$ to 10$\sp5$. Rates of axial water exchange at trivalent nickel centers vary from 10$\sp{7.5}$ M$\sp{-1}$s$\sp{-1}$ for tripeptides to greater than 10$\sp9$ M$\sp{-1}$s$\sp{-1}$ for tripeptideamides and macrocycles. Axial exchange rates are correlated with EPR data.
Degree
Ph.D.
Advisors
Margerum, Purdue University.
Subject Area
Analytical chemistry
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