Who we are

Multifunctional Luminescent Materials Group (Grupa Wielofunkcyjnych Materiałów Luminescencyjnych), established by Dr. Szymon Chorąży, belongs to the Faculty of Chemistry of Jagiellonian University in Kraków (Poland). Our research interests cover the design, synthesis, and thorough physicochemical characterization of diversely functionalized luminescent materials mainly based on metal complexes, with particular attention given to coordination assemblies exploring cyanido (CN) ligands as intermetallic molecular bridges.

Our Goal

We aim at the new generations of luminescent materials that combine light emission phenomena with various physical functionalities and property-generating features, including magnetic effects (magnetic ordering, molecular nanomagnetism), electric properties (switchable dielectric constant, ferroelectricity, ionic conductivity), non-centrosymmetricity and chirality (for non-linear optical properties and chiroptical effects), and sensitivity to physical (temperature, pressure, electric and magnetic fields, light irradiation, etc.) and chemical stimuli (solvents, gases, guest molecules). We are trying to develop unique synthetic strategies for multifunctional luminophores, such as luminescent molecular nanomagnets, emissive molecular ferroelectrics, luminescent proton conductors, chiral luminophores, porous emissive systems, and stimuli-responsive optical and multifunctional opto-electro-magnetic systems. We aim at linking the advantages of luminescent materials, applicable in light-emitting devices, optical communication, photovoltaics, sensors, or bioimaging, with new application horizons originating from the additional physical properties, such as nanomagnetism for high-density data storage devices with the optical output or porosity for highly-sensitive luminescent sensors.

Our Approach

Our main approach is based on the implementation of diverse physical properties within single-phase materials designable at the molecular level. As the result, such materials should become the tool for optical, magnetic, electronic, and multifunctional devices linking high performance with extreme miniaturization. Our group conducts all stages of the research, from the rational design and synthesis, through basic physicochemical characterization, structural studies, up to advanced physical experiments related to optical, magnetic, and electric properties, their combinations, and sensitivity of all these effects to external stimuli within multi-stimuli-responsive systems. We also support the obtained experimental results by theoretical calculations including ab initio and DFT methods.

Our current research interests include:

1. Luminescent  lanthanide single-molecule magnets

Trivalent lanthanide ions implemented into a suitable coordination environment can combine strong magnetic anisotropy and efficient photoluminescence in the visible-to-NIR range. Therefore, they are great candidates both for single-molecule magnets (SMMs) that are magnetic objects revealing a magnetic memory effect at the molecular level as well as for smart luminophores showing various light-emitting functionalities, including sensitized luminescence, up-conversion, quantum cutting, and many others. Our group focuses on luminescent SMMs searching for rational synthetic pathways resulting in strong magnetic anisotropy and enhanced photoluminescence. To achieve this goal we employ 4f metal ions and incorporate them into heterometallic coordination assemblies with non-innocent polycyanidometallates of transition metals. Resulting bifunctional magneto-luminescent systems can exhibit a broad set of optical and magnetic functionalities. These properties can be correlated, while possible interactions open routes for the switching of light emission by an external magnetic field and for magnetic memories exploring precise optical output. The representative examples from our group include white-light emissive dysprosium(III) SMMs governed by hexacyanidocobaltate(III) metalloligands (Chem. Eur. J. 2016, 22, 7371; left side) or dinuclear dysprosium(III)–cobalt(III) and dysprosium(III)–rhodium(III) molecules exhibiting the transition-metal-dependent tuning of magnetic and optical properties (J. Mater. Chem. C 2018, 6, 473; right side).

2. Multifunctional lanthanide-based materials

Lanthanide complexes not only offer tunable magnetic anisotropy and diversity of luminescent phenomena but also are promising prerequisites for the construction of multifunctional molecule-based materials. By linking 4f metal ions with organic ligands and cyanido complexes of transition metals within a single-phase material, it is possible to combine magnetic properties, such as single-molecule magnet (SMM) behavior, with luminescent effects (e.g. luminescent thermometric effect), and even additional physical phenomena, including proton conductivity or second-harmonic generation (SHG) activity. In MLMG, we work on the rational design of such multifunctional molecular materials that can realize the multi-tasking concept at the molecular level, having also the potential to exhibit unique cross-effects originating from the interaction between introduced properties. Therefore, they are great candidates for new generations of smart high-performance magnetic, optical, and electronic devices, as well as multifunctional opto-electro-magnetic systems. Our work within this field resulted in unprecedented examples of multifunctional materials, including proton-conductive luminescent thermometer based on near-infrared-emissive ytterbium(III)–cobalt(III) molecular nanomagnets (J. Am. Chem. Soc. 2020, 142, 3970; left side) as well as layered neodymium(III)–molybdenum(IV) and neodymium(III)–tungsten(IV) frameworks showing the transition-metal-dependent combination of SHG activity, sensitized NIR emission, and SMM characteristics (J. Mater. Chem. C 2021, 8, 10705; right side).

3. Luminescent thermometers

Optical thermometry based on thermally activated luminescence of f- and d-block metal ions or organic species is extensively investigated as it opens the pathways towards highly efficient contactless temperature sensors for medical diagnostics, micro-/nanoelectronics, and chemical reactors. The molecular approach in the construction of luminescent thermometers is of particular interest due to the desired sensing ability at the nanoscale. Our group searches for novel strategies towards luminescent thermometers showing the best possible thermometric parameters that can be realized by playing with the thermal variation of emissive electronic transitions of d-block, lanthanide, or actinide metal complexes, as well as organic ligands and guest molecules, all embedded in coordination or supramolecular frameworks. Our special attention is given to the application of cyanido metal complexes in the generation of efficient thermometric behavior. We also aim at the construction of multifunctional luminescent thermometers, for instance, optical thermometers based on single-molecule magnets (SMMs) which are promising candidates for smart electromagnetic SMM-based devices with a self-monitored temperature. The representative examples of luminescent thermometers from our group include layered terbium(III)/dysprosium(III)–cobalt(III) frameworks showing impressive colorimetric and ratiometric responses to temperature (J. Mater. Chem. C 2018, 6, 8372; left side) and the series of molecular holmium(III)–hexacyanidometallate(III) systems linking tunable SMM features with optical thermometry based on the luminescent re-absorption effect (Chem. Sci. 2021, 12, 730; right side).

4. Microporous luminophores

Porous coordination polymers and metal-organic frameworks (MOFs) were found to be promising for gas and energy storage, as well as molecular separation and purification. When microporosity within coordination frameworks is combined with distinct luminescence, their application horizon is broadened towards optical sensing of gases, solvents, and many other molecules, including contaminants, explosives, biological species, or pharmaceuticals. Moreover, the porosity of coordination systems, as well as the sensitivity of dynamic non-porous molecular materials to solvent exchange, enables the switching of their intrinsic properties. For instance, microporous magnets exhibit magnetic behavior modifiable by the reversible uptake of solvent that can be employed in the optimization of magnetic performance or the construction of advanced magnetic switches. In MLMG, we show interest in the combination of responsivity of the material to solvent exchange and other chemical stimuli with photoluminescence within coordination systems based on cyanido metal complexes. We also consider other physical properties that can be incorporated in porous luminophores based on polycyanidometallates to achieve a higher level of multifunctionality. In this context, we presented dehydration–hydration switching of visible luminescence and Single-Molecule Magnet behavior in three-dimensional dysprosium(III)–cobalt(III) network (J. Am. Chem. Soc. 2019, 141, 18211; left side) as well as the correlated solvent and temperature impacts on the luminescence of Hofmann-type strontium(II)–rhenium(V) MOF (Inorg. Chem. 2021, 60, 4093; right side).

5. Emissive non-canonical Prussian Blue Analogs

Classical Prussian Blue Analogs (PBAs) consist of three-dimensional purely inorganic coordination polymers based on hexacyanidometallates of d-block metal ions combined with the second transition metal centers. PBAs offer a remarkable platform for achieving valuable physical effects, including room-temperature magnetic ordering, photomagnetism, magnetization-induced SHG activity, high permanent porosity, super-ionic conductivity, ferroelectricity, etc. Considerable attention is also given to PBA-like frameworks composed of hexacyanidometallates and f-block metal ions that can link the intrinsic properties of lanthanides or actinides, such as strong photoluminescence and magnetic anisotropy, with the effects related to cyanido complexes, such as photomagnetism or negative thermal expansion. Therefore, they are promising platforms for multifunctional luminescent materials. We follow this idea searching for novel emissive PBA-like d-f coordination assemblies. The representative examples of our work in this field include hybrid organic-inorganic uranyl(VI)–hexacyanidometallate(III,IV) frameworks exhibiting multicolor photoluminescence efficiently tuned by the d-block-metal exchange within cyanido transition metal complex (Chem. Commun. 2019, 55, 3057; left side) and non-centrosymmetric dysprosium(III)–copper(I) and ytterbium(III)–copper(I) networks incorporating visible- or NIR-emissive lanthanide Single-Molecule Magnets (Chem. Eur. J. 2019, 25, 11820; right side).

6. Cyanido-bridged molecular magnetic assemblies

Cyanido complexes of d-block metal ions are efficient molecular building blocks for the construction of magnetic coordination frameworks and clusters exhibiting a variety of physical phenomena including long-range magnetic ordering of high critical temperatures, photoinduced spontaneous magnetization, multi-stimuli-responsive charge transfer and spin crossover effects, or strong magnetic anisotropy. All these prerequisites made polycyanidometallate-based systems attractive candidates for applications in magnetic, optical, and opto-magnetic memory devices, spintronics, and quantum computation, as well as high-performance sensors of physical and chemical stimuli. They form also a promising platform for the implementation of multifunctionality towards such advanced materials as proton conductive magnets or molecular multiferroics. In this regard, our work is focused on searching for unique cyanido-bridged molecular assemblies that are able to show the unprecedented combinations of magnetic effects with other physical properties and the controlled responsivity to external stimuli. Our particular attention is paid to the exploration of octacyanidorhenate(V) ion as an advanced metalloligand for heterometallic iron(II)-rhenium(V) spin crossover (SCO) materials. This research pathway can be illustrated by our reports on iron(II)-based thermally-induced SCO effect occurring selectively for the inner 3d metal center of the nanosized pentadecanuclear {FeII9[ReV(CN)8]6} cluster (Angew. Chem. Int. Ed. 2015, 54, 5093; left side) and multi-step hysteretic thermal SCO effect switchable by temperature, light, and pressure in the layered iron(II)–rhenium(V) framework (Angew. Chem. Int. Ed. 2020, 59, 15741; right side).

7. Theoretical studies of magnetic and luminescent properties of functional solids

The understanding of magnetic and luminescent effects in functional materials requires combining numerous experimental and theoretical methods. For luminophores based on metal complexes, the theoretical studies are usually realized using DFT and TD-DFT methods within molecular and/or periodic limitations. On the other hand, single-molecule magnets, in particular those based on lanthanide(III) complexes, can be thoroughly investigated using ab initio calculations of a CASSCF/RASSI/SINGLE_ANISO type; however, this type of calculations can be also employed to some extent for the elucidation of emission spectra. In MLMG, we focus on the application and optimization of theoretical methods, including both ab initio as well as DFT approaches, in the investigation of magnetic and luminescent properties of multifunctional luminescent materials obtained by our group. For instance, we have presented the combined methodology involving both experimental and ab initio methods for rationalization of magneto-luminescent properties within a family of ytterbium(III) molecular nanomagnets embedded in cyanido/thiocyanidometallate-based crystalline materials (J. Phys. Chem. Lett. 2021, 12, 10558; see below). Our work is also devoted to the development of computational methods and software for the convenient analysis of experimental data as exemplified by the relACs program enabling efficient analysis of the alternate-current (ac) magnetic data (see the section relACs).

2021 Multifunctional Luminescent Materials Group
Faculty of Chemistry | Jagiellonian University