The introduction of fluorine atoms into molecules and materials across many fields of academic and industrial research is now commonplace, owing to their unique properties. A particularly interesting feature is the impact of fluorine substitution on the relative orientation of a C−F bond when incorporated into organic molecules. In this Review, we will be discussing the conformational behavior of fluorinated aliphatic carbo‐ and heterocyclic systems. The conformational preference of each system is associated with various interactions introduced by fluorine substitution such as charge‐dipole, dipole‐dipole, and hyperconjugative interactions. The contribution of each interaction on the stabilization of the fluorinated alicyclic system, which manifests itself in low conformations, will be discussed in detail. The novelty of this feature will be demonstrated by presenting the most recent applications.

Benzannulated bidentate pyridine/phosphine ( P^N) ligands bearing quinoline or phenanthridine (3,4-benzoquinoline) units have been prepared, along with their halide-bridged, dimeric Cu(I) complexes of the form [( P^N)Cu](μ-X). The copper complexes are phosphorescent in the orange-red region of the spectrum in the solid-state under ambient conditions. Structural characterization in solution and the solid-state reveals a flexible conformational landscape, with both diamond-like and butterfly motifs available to the CuX cores. Comparing the photophysical properties of complexes of (quinolinyl)phosphine ligands with those of π-extended (phenanthridinyl)phosphines has revealed a counterintuitive impact of site-selective benzannulation. Contrary to conventional assumptions regarding π-extension and a bathochromic shift in the lowest energy absorption maxima, a blue shift of nearly 40 nm in the emission wavelength is observed for the complexes with larger ligand π-systems, which is assigned as phosphorescence on the basis of emission energies and lifetimes. Comparison of the ground-state and triplet excited state structures optimized from DFT and TD-DFT calculations allows attribution of this effect to a greater rigidity for the benzannulated complexes resulting in a higher energy emissive triplet state, rather than significant perturbation of orbital energies. This study reveals that ligand structure can impact photophysical properties for emissive molecules by influencing their structural rigidity, in addition to their electronic structure.

A synthetic route to 4-bromophenanthridine has been devised, enabling the construction of (4-diphenylphosphino)phenanthridine (1), a heterobifunctional Lewis base containing both phosphine and phenanthridine donors. The coordination chemistry of 1 with ions of late first-row transition metals nickel, copper and zinc has been explored, leading to the isolation and characterization of an organometallic Ni(II) complex, chloro(1-naphthyl)[(4diphenylphosphino)phenanthridine]nickel (2), a halide-bridged copper(I) complex, bromo[(4-diphenylphosphino)phenanthridine]copper dimer (3), and a Zn(II) complex, bis(chloro) [(4-diphenylphosphino)phenanthridine]zinc (4). The solid-state structures of 2-4 demonstrate the ability of 1 to support both square planar and tetrahedral geometries. Electrochemical and luminescence studies revealed both metal and ligand-based redox activity and emissive properties.

A ruthenium hydrido chloride complex (1) supported by a simple, heteroleptic bidentate P^N ligand (L1) containing a diarylphosphine and a benzannulated phenanthridine donor arm is reported. In the presence of base, complex 1 catalyzes multi-component reactions using alcohol precursors to produce structurally diverse molecules including pyridines, quinolines and pyrimidines via acceptorless dehydrogenative coupling pathways. Notably, L1 does not bear readily (de)protonated Brønsted acidic or basic groups common to transition metal catalysts capable of these sorts of transformations, suggesting metal-ligand cooperativity does not play a significant role in the catalytic reactivity of 1. A rare example of an h 2 -aldehyde adduct of ruthenium was isolated and structurally characterized, and its role in acceptorless dehydrogenative coupling reactions is discussed.

Turn it up! Inter-ion interactions and ligand design can synergistically boost emission from Cu(i) complexes, tuning from orange to yellow.