External electric fields drive the formation of P → C dative bonds

Chemical interactions driven by external electric fields (EFs) can serve as a catalytic force for molecular machines and linkers for smart materials. In this context, the EF-driven dative bond is demonstrated through the study of interactions between PH₃ and curved carbon-based nanostructures. The P → C dative bonds emerge only in the presence of EFs, whereas the interactions in the absence of EFs lead to van der Waals (vdW) complexes. The formation of EF-driven dative bonds can be verified with distinctive signals in vibrational, carbon-13 NMR, and UV/vis spectra. The nature of EF-driven dative bonds was theoretically analyzed with the block-localized wavefunction (BLW) method and the associated energy decomposition (BLW-ED) approach. It was found that the charge transfer interaction plays a dominating role and that even in the presence of EFs, complexes dissociate to monomers once the charge transfer interaction is "turned off". Notably, the inter-fragment orbital mixing stabilizes the complexes and alters their multipoles, leading to additional stability through field-multipole interactions. This conclusion was supported by further decomposition of the charge transfer energy component, clarifying the precise role of orbital mixing. The inter-fragment orbital mixing, which occurs exclusively in the presence of EFs, was elucidated using "<i>in situ</i>" orbital correlation diagrams. Specifically, both external EFs and intermolecular perturbations remarkably reduce the energy gap between the frontier orbitals of the monomers, thereby facilitating inter-fragment orbital interactions. Significant covalency was confirmed through <i>ab initio</i> valence bond (VB) theory calculations of the EF-driven dative bonds, aligning with the crucial role of the charge transfer interaction. This pronounced covalency emerges as a key feature of EF-driven interactions, setting them apart from traditional dative bonds studied in parallel throughout this work.