Mechanochromic Luminescence of N,N′-Dioxide-4,4′-bipyridine Bismuth Coordination Polymers

Abstract

The association of Bi 3+ ions and N,N′-dioxide-4,4′bipyridine (bp4do) ligands has led to three related compounds [Bi 2 Br 6 (bp4do)(dmso) 4 ] (1), [BiBr 3 (bp4do)(dmso)] (2), and [Bi 2 Br 6 (bp4do) 3 ] (3). 2 can be described from 1, and 3 from 2, by the substitution of two dmso molecules by one bp4do molecule, the octahedral geometry of bismuth ions being kept as BiBr 3 O-(bp4do)O 2 (dmso) in 1, BiBr 3 O 2 (bp4do)O(dmso) in 2, and BiBr 3 O 3 (bp4do) in 3. In the absorption spectra of 1−3, as well as Bi/bp4do complexes in solution, a metal-to-ligand charge transfer band is observed as a result of the formation of Bi−O(Noxide) bonds. All 1−3 materials exhibit luminescence properties of phosphorescence type with quantum yields up to 54% for 1. In contrast with 1 (isolated complexes in the solid state), 1D coordination polymer type compounds 2 and 3 exhibit mechanochromic luminescence (MCL) properties: upon grindinga few seconds for 2the broad emission bands of the pristine compounds centered at 575 nm (2, yellow emission) and 600 nm (3, orange emission) are shifted by 75 nm (2) or 50 nm (3) (bands centered at 650 nm), leading to a strong red emission, whereas the process is reversible by heating, fuming, or recrystallization in a few drops of solvent. These MCL properties of 2 and 3 may be related to conformational changes of polymeric chains upon grinding.

[213Bi]Bi3+/[111In]In3+-neunpa-cycMSH: Theranostic Radiopharmaceutical Targeting Melanoma─Structural, Radiochemical, and Biological Evaluation

“…43−45 Large-core relativistic effective core potentials (LCRECP) and the associated valence basis sets were used for modeling of Bi 3+ , while light atoms (C, H, N, O) were treated up to Def2TZVP levels of theory. 43,46 The conformational isomers of [Bi(neunpa-NH 3 )] were investigated through geometric optimizations in aqueous solution using the PCM solvation model and vibrational frequency analysis of their local energy minima.…”

Structure–Property Relationships in Photoluminescent Bismuth Halide Organic Hybrid Materials

“…The numbers of bound chloride ligands per Bi metal center are three, one, and one for 2 , 3A-Cl and 3B-Cl , respectively. While visible excitation has been achieved in several other Bi halide hybrid materials, the origin of these transitions, as well as the resultant emission, has been difficult to discern from photoluminescent data alone. , The photoluminescent behavior of bismuth-based materials has been attributed to a number of pathways including metal centered (MC) transitions, metal-to-ligand/ligand-to-metal charge transfer (MLCT/LMCT), and/or intra- or interligand charge transfer (ILCT/LLCT). ,− , Thus, in an effort to identify the transitions, orbital contributions, and corresponding structural motifs that underlie the luminescence observed for 2 , 3A-Cl , 3A-Br , 3B-Cl , 4 , and 6 as well as elucidate trends in the observed PL spectra, parallel computational efforts were employed.…”

“…It is worth noting that similar XMLCT pathways serving as intermediate energy states have recently been observed in Biand Sb-halide materials. 59,76,77 Botta and colleagues, for example, reported several BiBr-dioxide pyridine coordination polymers that display mechanochromism, for which the excitation and emission are attributed to XMLCT and inverse LXMCT pathways, respectively. 23,31,59 These energy transfer pathways were assigned primarily to higher energy absorption features (λ = < 350 nm), yet visible excitation features are often present as well.…”

“…59,76,77 Botta and colleagues, for example, reported several BiBr-dioxide pyridine coordination polymers that display mechanochromism, for which the excitation and emission are attributed to XMLCT and inverse LXMCT pathways, respectively. 23,31,59 These energy transfer pathways were assigned primarily to higher energy absorption features (λ = < 350 nm), yet visible excitation features are often present as well. These previously reported materials possess three or more Br ions per Bi metal center and excitation bands that extend well beyond 500 nm.…”

π-Stacking Conversion and Enhanced Force-Stimuli Response of a Divinylanthracene Derivative in a Hydrogen-Bonded Framework

“…It is well-known that the hydrogen bond (H-bond) as strong intermolecular interaction is also a powerful means to construct functional supramolecular systems by offering multiple weak secondary interactions to control molecular arrangement or stabilize special conformation. − The H-bond has been utilized to construct cocrystals with excellent and controllable luminescent properties. − Moreover, intermolecular hydrogen bonds could convert the π-stacking model to enhance or improve the specific functions of the self-assembled system. − Recently, organic materials in response to mechanical forces have attracted widespread attention because of their wide applications in electronic devices, optical data storage, pressure sensors, and security. − These materials can change their charge, luminescence, conductivity, and shape under force stimuli. Specifically, those organic molecules may change their color or luminescent properties through a process called mechanochromism (MC), because their molecular structures or aggregate types are different before and after mechanical force stimuli. − However, the research on how the intermolecular hydrogen bond regulates the mechanochromic property of the hydrogen-bonded eutectic system is still rather rare , and is worth studying.…”