Carbon-based lewis acids and carbodications : computational studies on structure, stabilisation, and lewis acidity

RWTH Publications (RWTH Aachen)

Abstract

This thesis examines carbon-centred cationic species as Lewis acids, with a particular focus on carbocations, carbodications, and related highly electron-deficient carbon frameworks. The work focuses on computational investigations to clarify how charge, valency, donor stabilisation, and molecular structure influence the stability and Lewis acidity of carbon-based acceptors. The thesis is divided into four main chapters. Chapter I introduces carbon-based Lewis acids, beginning with carbocations and tritylium ions as established examples, before moving to carbodications as more highly electron-deficient carbon frameworks. Chapter II presents a systematic computational study of CHx±n species across different hydrogenation states, charge states, and spin multiplicities, providing a reference map for unusual carbon valence and charge states. Chapter III investigates donor-supported geminal carbodication models based on N-heterocyclic imine and N-heterocyclic olefin donors, with emphasis on the relationship between donor identity, charge distribution, bonding, and Lewis acidity. Chapter Ⅳ addresses the quantification of double Lewis acidity in dicationic acceptors by comparing fluoride- and oxide-based ion affinity descriptors. Together, these researches aim to connect the conceptual chemistry of carbocations and carbodications with molecular design principles and quantitative descriptors. The broader goal is to contribute to a clearer understanding of how highly electron-deficient carbon-based Lewis acids can be stabilised without suppressing their characteristic reactivity.

Authors 1

1. Yiwei Gong corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen