# Temperature‑, Concentration‑, and Solvent-Dependent M/P Helicity Switching of Double-Helical Monometallofoldamers with Inversion of Circularly Polarized Luminescence

## TL;DR

Scientists created a fluorescent molecule that can switch its helical shape and light polarization in response to changes in solvent, temperature, and concentration.

## Contribution

A new double-helical metallofoldamer is introduced that enables controllable helicity and CPL inversion through environmental stimuli.

## Key findings

- The complex [(R)-Ag(1c)2][PF6] showed positive CPL in CH2Cl2 and negative CPL in toluene.
- CPL inversion was triggered by temperature- and concentration-dependent aggregation in polar solvents.

## Abstract

Fluorescent double-helical monometallofoldamers [Ag­(1)2]­[PF6] were constructed by the mononuclear
complexation of two bipyridine strands 1 featuring two
L-shaped dibenzopyrrolo­[1,2-a]­[1,8]­naphthyridine
units at both ends with a Ag­(I) cation. These monometallofoldamers
exhibited double-helical/open conformational switching. [(R)-Ag­(1c)2]­[PF6] with
chiral side chains induced a single-handed helix sense and enabled
precise control of M/P helicity
switching in response to a solvent. This complex also exhibited strong
fluorescence and circularly polarized luminescence (CPL) inversion
switching upon M/P helicity inversion.
For instance, [(R)-Ag­(1c)2]­[PF6] exhibited positive CPL in CH2Cl2 (φF = 0.69, g
lum = 1.9 × 10–3) and negative CPL in toluene
(φF = 0.79, g
lum = −2.0
× 10–3). This double helix also aggregated
in polar solvents, which led to CPL inversion switching induced by
temperature- and concentration-dependent aggregation.