The series of osmium(ii) complexes [Os(bpy)_3−n(btz)_n][PF₆]₂(bpy = 2,2′-bipyridyl, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl,1 n= 0,2 n= 1,3 n= 2,4 n= 3), have been prepared, characterised and used as phosphors within light-emitting electrochemical cells.

A new “click” ligand, 2,6-bis(1-(pyridin-4-ylmethyl)-1H-1,2,3-triazol-4-yl)pyridine (L) featuring a tridentate 2,6-bis(1,2,3-triazol-4-yl)pyridine (tripy) pocket and two pyridyl (py) units was synthesized in modest yield (42%) using the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The coordination chemistry of the ligand with silver(I) and iron(II) ions was examined using a battery of solution (¹H and DOSY (diffusion ordered spectroscopy) nuclear magnetic resonance (NMR), infrared and absorption spectroscopies, high-resolution electrospray ionization mass spectrometry (HR-ESI-MS)), and solid state (X-ray crystallography, elemental analysis) techniques. When treated with silver(I) ions, the ligand forms discrete [Ag(L)]⁺ (X⁻, where X⁻ = BF₄⁻, NO₃⁻ or SbF₆⁻) complexes in dimethyl sulfoxide (DMSO) solution but these complexes crystallize as coordination polymers. The addition of [Fe(H₂O)₆](BF₄)₂ to an acetonitrile solution of the ligand forms the expected monomeric octahedral [Fe(L)₂]²⁺ complex and treatment of the iron(II) complex with AgBF₄ generates a heterometallic linear coordination polymer.

Four new heteroleptic copper(I) complexes bearing either 2-pyridyl-1,2,3-triazole (pytri) or the related triphenylamine (TPA) substituted (TPApytri) ligands and the ancillary ligands 6,6′-dimesityl-2,2′-bipyridine (diMesbpy) or bis[(2-diphenylphosphino)phenyl] ether (POP) were synthesized in good yields (75-95%). All the complexes were extensively characterized using nuclear magnetic resonance (NMR) spectroscopies and electrospray ionization mass spectrometry (ESIMS) and in the case of the two pytri compounds the solid state structures were determined via X-ray crystallography. The pytri complexes showed MLCT absorption bands which shift from 433 nm for the diMesbpy complex to 347 nm for POP. TPA-pytri complexes introduce an ILCT band resulting in improved visible absorption (376 nm, 26400 M⁻¹ cm⁻¹ for [Cu(TPA-pytri)(diMesbpy)](PF₆)). Emission from this ILCT state (470 nm, Φ = 0.08) was redshifted compared to the free ligand with negligible effects from ancillary ligands. Band assignments were confirmed with resonance Raman spectroscopy and TD-DFT calculations.

Three ferrocene‐based rotary switches featuring 2‐pyridyl‐1,2,3‐triazole (pytri) “click” chelates have been developed. The rotors can be switched from a folded (syn) to extended (anti) conformation by the addition of [Cu(CH₃CN)₄](PF₆) and 6,6′‐dimesityl‐2,2′‐bipyridine. This extension process could be reversed by the addition of 1,4,8,11‐tetraazacyclotetradecane (cyclam) to sequester the Cu(I) ions. Disappointingly, the weakness of the pytri chelates prevented the development of an electrochemically switchable system.