Browsing by Author "Eskelinen, Toni"
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- Bismuth as a Z-Type Ligand: an Unsupported Pt−Bi Donor-Acceptor Interaction and its Umpolung by Reaction with H2
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-10-07) Schwarzmann, Johannes; Eskelinen, Toni; Reith, Sascha; Ramler, Jacqueline; Karttunen, Antti J.; Poater, Jordi; Lichtenberg, CrispinEstablishing unprecedented types of bonding interactions is one of the fundamental challenges in synthetic chemistry, paving the way to new (electronic) structures, physicochemical properties, and reactivity. In this context, unsupported element-element interactions are particularly noteworthy since they offer pristine scientific information about the newly identified structural motif. Here we report the synthesis, isolation, and full characterization of the heterobimetallic Bi/Pt compound [Pt(PCy3)2(BiMe2)(SbF6)] (1), bearing the first unsupported transition metal→bismuth donor/acceptor interaction as its key structural motif. 1 is surprisingly robust, its electronic spectra are interpreted in a fully relativistic approach, and it reveals an unprecedented reactivity towards H2. - Cyanido-bridged diplatinum(ii) complexes: ligand and solvent effect on aggregation and luminescence
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-03-21) Khistiaeva, Viktoria V.; Buss, Stefan; Eskelinen, Toni; Hirva, Pipsa; Kinnunen, Niko; Friedel, Joshua; Kletsch, Lukas; Klein, Axel; Strassert, Cristian A.; Koshevoy, Igor O.The association of platinum(ii)-based luminophores, which is caused by metal⋯metal and π-π stacking interactions, has been actively exploited in supramolecular construction of photofunctional molecular materials. Herein, we describe a series of bimetallic complexes [{Pt(C^N^ /*N)} 2(CN)][BAr 4 F], containing cyanido-bridged cyclometalated Pt(ii) chromophore fragments (HC^N^N = 6-phenyl-2,2′-bipyridine, (benzyltriazolyl)-phenylpyridine, and pyrazolyl-phenylpyridine; HC^N*N = N-pentyl-6-phenyl-N-(pyridin-2-yl)pyridin-2-amine; ^/* denote five/six-membered metallocycles). These compounds are intensely phosphorescent at room temperature showing quantum yields up to 0.73 in solution and 0.62 in the solid state, which are generally higher than those of the mononuclear relatives [Pt(C^N^ /*N)(CN)]. The complex cations bearing sterically unhindered −C^N^N ligands readily assemble in solution, reaching the tetrameric species [{Pt(C^N^N)} 2(CN)] 4 4+ as suggested by diffusion NMR spectroscopy. The size of the aggregates can be regulated by the concentration, temperature, and polarity of the solvent that allows to alter the emission from green to near-IR. In the solid state, the maximum of low-energy luminescence is shifted up to 912 nm. The results show that photophysical properties of discrete complexes and the intermolecular aggregation can be substantially enhanced by utilizing the rigid bimetallic units giving rise to novel dynamic light emitting Pt(ii) systems. - Fast and Tunable Phosphorescence from Organic Ionic Crystals
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-09-04) Partanen, Iida; Al-Saedy, Omar; Eskelinen, Toni; Karttunen, Antti J.; Saarinen, Jarkko J.; Mrózek, Ondrej; Steffen, Andreas; Belyaev, Andrey; Chou, Pi-Tai; Koshevoy, Igor O.Crystalline diphosphonium iodides [MeR2P-spacer-R2Me]I with phenylene (1, 2), naphthalene (3, 4), biphenyl (5) and anthracene (6) as aromatic spacers, are photoemissive under ambient conditions. The emission colors (λem values from 550 to 880 nm) and intensities (Φem reaching 0.75) are defined by the composition and substitution geometry of the central conjugated chromophore motif, and the anion-π interactions. Time-resolved and variable-temperature luminescence studies suggest phosphorescence for all the titled compounds, which demonstrate observed lifetimes of 0.46–92.23 μs at 297 K. Radiative rate constants kr as high as 2.8×105 s−1 deduced for salts 1–3 were assigned to strong spin-orbit coupling enhanced by an external heavy atom effect arising from the anion-π charge-transfer character of the triplet excited state. These rates of anomalously fast metal-free phosphorescence are comparable to those of transition metal complexes and organic luminophores that utilize triplet excitons via a thermally activated delayed fluorescence mechanism, making such ionic luminophores a new paradigm for the design of photofunctional and responsive molecular materials. - Hybrid Inorganic-Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-12-05) Temerova, Diana; Chou, Tai Che; Kisel, Kristina S.; Eskelinen, Toni; Kinnunen, Niko; Jänis, Janne; Karttunen, Antti J.; Chou, Pi-Tai; Koshevoy, Igor O.The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, LP +Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic-organic zero-dimensional compounds [ LP +ZnBr2]2[ZnBr4] ( 1 ) and [( LP +)2Cd2Br4][CdBr4] ( 2 ), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λem = 458 nm, φem = 0.11 for 1 ; λem = 460 nm, φem = 0.13 for 2 ). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr4]2- and MBr2 units. Contrary to ionic species 1 and 2 , lead(II) bromide affords a neutral and water-stable complex [( LP +)2Pb3Br8] ( 3 ), showing weak room-temperature phosphorescence arising from spin-orbit coupling due to the heavy atom effect. The emission, which is substantially enhanced for the amorphous sample of 3 (λem = 575 nm, φem = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials. - OLED-laitteiden emitterien eri sukupolvet ja kehitys
Kemiantekniikan korkeakoulu | Bachelor's thesis(2023-05-24) Hautojärvi, Sara - Ryhmän 11 metallien valoa tuottavat koordinaatiokompleksit
Kemiantekniikan korkeakoulu | Bachelor's thesis(2024-12-15) Reinikainen, PipsaTässä kandidaatin tutkielmassa perehdytään luminesenssin eri tyyppeihin ja mekanismeihin. Säteilevistä mekanismeista erityisesti kiinnitetään huomiota termoaktivoituun viivästyneeseen fluoresenssiin (TADF), ja käsitellään sen esiintyvyyttä ryhmän 11 metallikomplekseilla. Tavoitteena on tarkastella edellytyksiä TADF:n toiminnalle, ja sen etuja verrattuna muihin säteileviin mekanismeihin. Lisäksi tutkielmassa esitetään keinoja luminesenssin hyötysuhteen parantamiseksi sekä luminesenssin mahdollisia sovelluskohteita. Tutkielman yhteenvetona voidaan todeta termoaktivoidun viivästyneen fluoresenssin tarjoavan merkittäviä etuja säteilevänä mekanismina. TADF:n on mahdollista tapahtua tehokkaasti ilman raskasmetalleja, mikä tekee siitä ympäristöystävällisemmän ja kustannustehokkaamman vaihtoehdon. Luminesenssin hyötysuhde paranee, kun säteilemättömien siirtymien todennäköisyyttä pienennetään, jolloin suurempi osa eksitoneista osallistuu säteilevään siirtymään. TADF-materiaalit voivat RISC-prosessin avulla saavuttaa jopa 100 %:n hyötysuhteen, mikä tekee niistä erinomaisia sovelluksissa, joissa tarvitaan korkeaa luminesenssin tehokkuutta, kuten valaistuksessa ja näyttötekniikoissa. Tämän seurauksena TADF-teknologia avaa merkittäviä mahdollisuuksia energiatehokkuuden ja kestävän kehityksen tavoitteiden edistämiseen.