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.

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The inclusion compound of macrocyclic cavitand cucurbit [8]uril (CB[8]) with the nickel(II) complex containing the tetraazamacrocyclic ligand cyclam, {[Ni(cyclam)]@CB[8]}Cl 2 • •16H 2 O (1), and the inclusion compounds of CB[8] with the copper(II) bis ethylene diamine complex, {trans [Cu(en) 2 (H 2 O) 2 ]@CB[8]}Cl 2 •{CB[8]}•42H 2 O (2a) and {trans [Cu(en) 2 (H 2 O) 2 ]@CB[8]}Cl 2 •17H 2 O (2b), were synthesized and characterized by X ray diffraction analysis, IR and ESR spectroscopy, and electrospray mass spectrometry. Guest-host inclusion compounds can be directly synthesized starting from a metal complex and cucurbit[8]uril, as was exemplified by the preparation of compounds 2a and 2b.Transition metal complexes with polyamines are used as model compounds in studies of metal ion transport in biological systems, 1 for metal regeneration, 2 as NMR con trast agents, 3 for radioactive diagnostics, 4 etc. Metal com plexes with tetraazamacrocyclic ligands are of interest as highly promising materials for use in medicine 5 and as catalysts for various reactions, such as epoxidation or DNA hydrolysis. 6 Inclusion of metal complexes in large organic macro cycles is a rather rare phenomenon. Nevertheless, such compounds, particularly, those with transition metals, are of considerable interest because of a unique environment of the metal ions, which is similar to that observed in metalloenzymes. The first inclusion compounds of macro cycles with metal complexes were synthesized in the late 1980s. 7 In these compounds, alkali metal complexes with crown ethers and cryptands are included in the γ cyclodextrin cavity. For transition metals, an example of inclusion compounds is the zinc pyridylporphyrin com plex included in a macrocycle formed by four other por phyrin complexes. 8 Earlier, inclusion compounds of tran sition metal complexes with polyamines have been syn thesized in the only study, 9 where the inclusion of copper(II) and zinc(II) complexes with the tetraaza macrocyclic ligands cyclam (cyclam is 1,4,8,11 tetraaza cyclotetradecane) and cyclen (cyclen is 1,4,7,10 tetraaza cyclododecane) in the cavity of the organic macrocyclic cavitand cucurbit[8]uril (CB[8]) was described.Cucurbit[n]urils (CB[n]) belong to a family of organic compounds with the composition C 6n H 6n N 4n O 2n . These compounds have a rigid macrocyclic structure consisting of n glycoluril fragments linked via 2n methylene bridges, where n = 5-10. 10,11 Since cucurbiturils have a large intramolecular cavity, they can serve as hosts and form inclusion compounds with guest molecules or ions of ap propriate size (methylpyridinium cations, 12 tetrahydrofu ran molecules, 13 PhP(O) 2 (OH) 14 ). Inclusion of two or more guest molecules in the cavity of large cucurbit[n]urils offers a unique possibility to study new forms of stereo isomerism, bimolecular reactions, and the molecular be havior in the microenvironment. 15, 16 Cucurbit[n]urils differ from other molecular contain ers with cavities of similar size, such as cyclodextrins and calixarenes, in the s...

Supramolecular compounds of the di , trideca , and triacontanuclear aluminum aqua hydroxo complexes, viz., [Al 2 (OH) 2 (H 2 O) 8 ] 4+ , [Al 12 (AlO 4 )(OH) 24 (H 2 O) 12 ] 7+ , and [Al 30 O 8 (OH) 56 (H 2 O) 26 ] 18+ , respectively, with the organic macrocyclic cavitand cucurbit[6]uril (C 36 H 36 N 24 O 12 ) were prepared by evaporation of aqueous solutions of aluminum nitrate and cucurbit[6]uril after the addition of pyridine, ammonia, KOH, or NaOH at pH 3.1-3.8. X ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril.