Isomer-specific reactivity is key in cluster chemistry. Herein, it is shown that how combining drift-tube ion mobility with mass spectrometry enables the derivation of reaction rate coefficients for coexisting C40+$\text{C}_{40}^{+}$ isomers, opening new avenues for studying complex chemical systems.

Distinguishing the chemical reactivity of isomers is a fundamental challenge in chemistry, particularly in cluster chemistry, where the number of possible structures increases dramatically with cluster size. This study presents a novel approach for measuring the kinetics of ion-molecule reactions of laser-ablated species in an isomer-specific fashion. This is achieved by combining drift-tube ion mobility with mass spectrometry, enabling shape selection prior to investigating the chemical reactivity of species of interest. First, the capability of obtaining reaction rate coefficients by studying the nucleophilic addition reactions of small monocyclic carbon rings (C11+$\text{C}_{11}^{+}$, C15+$\text{C}_{15}^{+}$, and C17+$\text{C}_{17}^{+}$) with pyridine, comparing the results with previously reported values is validated. Then the ability to determine isomer-specific reaction rate coefficients using the C40+$\text{C}_{40}^{+}$ cluster, where multiple isomers coexist is demonstrated. This highlights the potential of our new instrument for accurately characterizing isomer-specific reactivities in complex chemical systems.