From Coordination to π-Hole Chemistry of Transition Metals:Metalloporphyrins as a Case of Study

Abstract

[eng] Herein we have evidenced the formation of favorable π-hole Br···metal noncovalent interactions (NCIs)involving elements from groups 9, 11 and 12. More in detail, M (M=Co2+, Ni2+, Cu2+ and Zn2+) containing porphyrinshave been synthesized and their supramolecular assemblies structurally characterized by means of single crystal X-raydiffraction and Hirshfeld surface analyses, revealing the formation of directional Br···M contacts in addition to ancillaryhydrogen bond and lone pair-π bonds. Computations at the PBE0-D3/def2-TZVP level of theory revealed the π-holenature of the Br···M interaction. In addition, the physical nature of these NCIs was studied using Quantum Chemistrymethodologies, providing evidence of π-hole Spodium and Regium bonds in Zn2+ and Cu2+ porphyrins, in addition tounveiling the presence of a π-hole for group 9 (Co2+). On the other hand, group 10 (Ni2+) acted as both electron donorand acceptor moiety without showing an electropositive π-hole. Owing to the underexplored potential of π-holeinteractions in transition metal chemistry, we believe the results reported herein will be useful in supramolecularchemistry, organometallics, and solid-state chemistry by i) putting under the spotlight the π-hole chemistry involving firstrow transition metals and ii) unlocking a new tool to direct the self-assembly of metalloporphyrins