Unprecedented organic-inorganic hybrid complexes, [Mn(L)3]MnHal4, containing both four- and hexacoordinated Mn2+ ions were synthesized by reacting MnCl2 or MnBr2 with bis(phosphine oxide) ligands (L) such as dppmO2, dppeO2, and 2,3-bis(diphenylphosphinyl)-1,3-butadiene (dppbO2). In the [Mn(L)3]2+ cation of the complexes, the Mn2+ ion features a [MnO6] octahedral coordination environment (Oh), and the [MnHal4]2- anion adopts a tetrahedral geometry (Td). These "two-in-one" complexes exhibit strong long-lived luminescence (τav = 12-15 ms at 300 K) having interesting thermochromic behavior attributed to the thermal equilibrium between two emission bands. So, in an emission spectrum of the typical complex [Mn(dppbO2)3]MnBr4, the intense "red" (ca. 620 nm) and weak "green" (ca. 520 nm) bands, originating from Mn2+ ions in Oh and Td environments, respectively, are observed. Cooling from 300 to 77 K simultaneously leads to (i) redshift of both bands by ca. 20 nm, (ii) increasing their intensities, and (iii) causing a substantial change of their integral intensity ratio from about 4 : 1 to 2 : 1. As a result, the colour of the emission changes from orange (CIE 0.56, 0.45) at 300 K to deep red (CIE 0.62, 0.39) at 77 K. This behavior was rationalized using steady-state and time-resolved fluorescent spectroscopy at various temperatures. The high photoluminescence quantum yields (up to 61% at 300 K) and fascinating dual-emissive phosphorescence coupled with high thermal stability and solubility suggest a high potential of this novel class of emissive Mn2+ complexes as promising emitters for OLED devices and potential stimuli-responsive materials.

A suite of paddle-wheel shaped [Cu2(PymPPh2)3(Lan) n ]­(PF6)2 complexes showing efficient thermally activated delayed fluorescence (TADF) has been synthesized. In these complexes, Cu­(I) ions are P,N-bridged by three diphenyl­(2-pyrimidyl)­phosphine (PymPPh2, L) ligands in a “head-to-tail” fashion, and one or both metals are also capped by the ancillary ligand (Lan = MeOH, Me2CO, MeCN, PhCN). At ambient temperature, the solid complexes emit TADF with the quantum yield of up to 85% and the lifetimes of from 9.6 to 27 μs. The ancillary ligands, whose orbitals negligibly contribute to the radiative 1(M + L + Lan)­LCT state, remarkably adjust emission energies and ΔE(S1–T1) energy splitting magnitudes of the emitters obtained. Thus, depending on structure and/or number of the Lan molecules, the emission maxima vary from 500 to 563 nm, and the ΔE(S1–T1) gaps range 550–1100 cm–1. Such tunable TADF characteristics coupled with the excellent solubility and air-stability make the complexes presented to be promising TADF materials.

Remarkable solvation-induced emission enhancement is discovered on a new Ag(i) complex showing sky-blue thermally activated delayed fluorescence (TADF).

A series of Cu(i) halide complexes showing thermally activated delayed fluorescence (TADF) combined with room temperature phosphorescence are reported.

Manipulating the relaxation pathways of excited states and understanding mechanisms of photochemical reactions present important challenges in chemistry. Here we report a unique zinc(II) complex exhibiting unprecedented interplay between the excitation-wavelength-dependent emission, thermally activated delayed fluorescence (TADF) and excited state intramolecular proton transfer (ESIPT). The ESIPT process in the complex is favoured by a short intramolecular OH⋅⋅⋅N hydrogen bond. Synergy between the excitation-wavelength-dependent emission and ESIPT arises due to heavy zinc atom favouring intersystem crossing (isc). Reverse intersystem crossing (risc) and TADF are favoured by a narrow singlet-triplet gap, ΔE ≈10 kJ mol . These results provide the first insight into how a proton-transfer system can be modified to show a synergy between the excitation-wavelength-dependent emission, ESIPT and TADF. This strategy offers new perspectives for designing ESIPT and TADF emitters exhibiting tunable excitation-wavelength-dependent luminescence.

Scheme 2. Proton transfer in imidazole-based ESIPT-fluorophores.

The first example of a triply bridging (μ3‐P) phosphine ligand has been discovered in the crown‐shaped [Cu3(μ2‐Hal)3L] (Hal=Cl, Br, or I) complexes supported by tris[2‐(2‐pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ3‐P‐bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s‐orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λem=442–465 nm) with the quantum efficiency reaching 100 %. The complex [Cu3(μ2‐I)3L] also exhibits remarkable thermo‐ and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands.

A series of isoreticular Ag(I) luminescent metal− organic frameworks (LMOFs), {[Ag 2 L 2 (CH 3 CN) 2 ](X) 2 } n (X = ClO 4 , OTf, and BF 4 ), has been designed, exploiting diphenyl(2pyrazyl)phosphine (L) as a multidentate linker. At ambient temperature, these compounds emit a bright long-lived phosphorescence (λ em = 545−555 nm) with a quantum efficiency as high as 22%, which is the highest value for phosphorescent Ag-LMOFs. The prepared LMOFs also exhibit pronounced thermochromic luminescence, reversibly changing their emission color in the 300− 77 K range. These LMOFs also demonstrate prominent solvatoand vapochromic luminescence, which manifest as a reversible change in the emission properties during the removal and recovery of the coordinated and guest MeCN molecules, respectively. Moreover, we have discovered a reversible solvent-driven 3D-to-0D transformation of the framework {[Ag 2 L 2 (CH 3 CN) 2 ](ClO 4 ) 2 } n into a brightly emissive complex [Ag 4 L 4 (ClO 4 ) 4 ]. To the best of our knowledge, the compounds obtained are the first Ag-LMOFs that exhibit thermo-, solvato-, and vapochromic luminescence.