title: Hierarchy of Supramolecular Arrangements and Building Blocks: Inverted Paradigm of Crystal Engineering in the Unprecedented Metal Coordination of Methylene Blue.
abstract: The aromatic methylene blue cation (MB+) shows unprecedented ligand behavior in the X-ray structures of the trigonal-planar (TP) complexes MBMCl2(M = CuI, AgI). The two isostructural compounds were exclusively synthesized by grinding together methylene blue chloride and MCl solids. Only in the case of AuCl did the technique lead to a different, yet isoformular, AuIderivative with separated MB+and AuCl2-counterions and no direct N-Au linkage. While the density functional theory (DFT) molecular modeling failed in reproducing the isolated Cu and Ag complexes, the solid-state program CRYSTAL satisfactorily provided for Cu the correct TP building block associated with a highly compact π stacking of the MB+ligands. In this respect, the dispersion interactions, evaluated with the DFT functional, provide to the system an extra energy, which likely supports the unprecedented metal coordination of the MB+cation. The feature seems governed by subtle chemical factors, such as, for instance, the selected metal ion of the coinage triad. Thus, the electronically consistent AuIion does not form the analogous TP building block because of a looser supramolecular arrangement. In conclusion, while a given crystalline design is generally fixed by the nature of the building block, a peculiarly efficient supramolecular packing may stabilize an otherwise unattainable metal complex.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma , Area delle scienze 17/A, 43124 Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Canossa
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma , Area delle scienze 17/A, 43124 Parma, Italy.
authors.forename: Alessia
authors.identifier: http://orcid.org/0000-0001-5675-9372
authors.initials: A
authors.lastname: Bacchi
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma , Area delle scienze 17/A, 43124 Parma, Italy.|Consorzio Interuniversitario Reattività Chimica e Catalisi , Via Celsio Ulpiani 27, 70126 Bari, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Graiff
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma , Area delle scienze 17/A, 43124 Parma, Italy.|Consorzio Interuniversitario Reattività Chimica e Catalisi , Via Celsio Ulpiani 27, 70126 Bari, Italy.
authors.forename: Paolo
authors.identifier: http://orcid.org/0000-0002-6926-2928
authors.initials: P
authors.lastname: Pelagatti
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma , Area delle scienze 17/A, 43124 Parma, Italy.|Consorzio Interuniversitario Reattività Chimica e Catalisi , Via Celsio Ulpiani 27, 70126 Bari, Italy.
authors.forename: Giovanni
authors.identifier: http://orcid.org/0000-0002-7912-641X
authors.initials: G
authors.lastname: Predieri
authors.affiliation: CNR-ICCOM , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ienco
authors.affiliation: CNR-ICCOM , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Manca
authors.affiliation: CNR-ICCOM , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Mealli