title: Chameleon-like behaviour of cyclo[n]paraphenylenes in complexes with C70: on their impressive electronic and structural adaptability as probed by Raman spectroscopy.
abstract: A series of four 1 : 1 host-guest supramolecular complexes of [n]CPPs and C(70) have been analyzed by Raman spectroscopy in the solid state and complemented with the analysis of their spectroscopic responses under mechanical and thermal stresses. By following the frequency behaviour of the G and RBM modes we have found that [10]CPP in the [10]CPP@C(70) complex displays a more "ordered" structure. However, in [11]CPP@C(70), the nanoring becomes oval-shaped with closer contacts with the C(70) poles and less conformational restriction in the flattened region. By mechanical and thermal stresses we are able to modify the lying conformation of [10]CPP@C(70) towards a standing orientation. [11]CPP@C(70) resists pressure changes, although it tends to shift from the standing to the lying orientation by heating. As for the crystal cell, the [n]CPPs occupy the residual empty spaces while the main crystallographic positions are reserved for C(70). These are new examples of the impressive adaptability of the [n]CPP molecules to different physico-chemical environments, a chameleon-like property which reveals the delicate equilibrium provided by cyclic conjugation and ring strain.
authors.affiliation: MALTA-Consolider Team, Department of Physical Chemistry, Chemistry Faculty, University Complutense of Madrid, 28040 Madrid, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Peña Alvarez
authors.forename: Paula
authors.initials: P
authors.lastname: Mayorga Burrezo
authors.forename: Takahiro
authors.initials: T
authors.lastname: Iwamoto
authors.forename: Lili
authors.initials: L
authors.lastname: Qiu
authors.forename: Miklos
authors.initials: M
authors.lastname: Kertesz
authors.forename: Mercedes
authors.initials: M
authors.lastname: Taravillo
authors.forename: Valentín G
authors.initials: VG
authors.lastname: Baonza
authors.forename: Juan T
authors.initials: JT
authors.lastname: López Navarrete
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamago
authors.forename: Juan
authors.initials: J
authors.lastname: Casado