Benjamin Dietzek’s research while affiliated with Friedrich Schiller University Jena and other places

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Publications (395)


Red-to-Blue Triplet–Triplet Annihilation Upconversion for Calcium Sensing
  • Article

July 2024

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25 Reads

The Journal of Physical Chemistry Letters

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Tingxiang Yang

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Sylvestre Bonnet

Triplet–triplet annihilation upconversion is a bimolecular process converting low-energy photons into high-energy photons. Here, we report a calcium-sensing system working via triplet–triplet annihilation (TTA) upconverted emission. The probe itself was obtained by covalent conjugation of a blue emitter, perylene, with a calcium-chelating moiety, and it was sensitized by the red-light-absorbing photosensitizer palladium(II) tetraphenyltetrabenzoporphyrin (PdTPTBP). Sensing was selective for Ca²⁺ and occurred in the micromolar domain. In deoxygenated conditions, the TTA upconverted luminescence gradually appeared upon adding an increasing concentration of calcium ions, to reach a maximum upconversion quantum yield of 0.0020.


Fig. 2 Electrochemical data from cyclic voltammetry in 0.1 M n-Bu 4 NPF 6 THF solutions at a scan rate of 50 mV/s (dots); DFT-calculated frontier orbitals, and energies for [Pt(dpp)(PnPh 3 )] (left) and [Pt(dba)(PnPh 3 )] (right; Pn = P, As, Sb). Values for the redox potentials are half half-wave potentials E 1/2 for the reversible first reduction and potentials Ep for the irreversible oxidations and second and third reductions (Table S6, ESI †).
Fig. 6 Decomposition of the emissive T 1 states into MLCT, L'MCT, LL'CT, LC and MC contributions for [Pt(dpp)(PnPh 3 )] (left) and [Pt(dba)(PnPh 3 )] (right; Pn = P, As, Sb, Bi) based on TD-DFT calculations (TPSSh/def2-TZVP/CPCM(CH 2 Cl 2 )). 82
Fig. 7 Transient absorption spectra (TAS) at selected delay times (a to c) and decay-associated spectra (d to f) for [Pt(dpp)(SbPh 3 )] following excitation at 340 nm (a and d), [Pt(dba)(SbPh 3 )] upon excitation at 340 nm (b and e) and 500 nm (c and f) in THF. The thicker lines in TAS shows smoothed data.
Enhanced luminescence properties through heavy ancillary ligands in [Pt(C^N^C)(L)] complexes, L = AsPh3 and SbPh3
  • Article
  • Full-text available

November 2023

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130 Reads

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2 Citations

Dalton Transactions

In the frame of our research aiming to develop efficient triplet-emitting materials, we are exploring the concept of introducing additional heavy atoms into cyclometalated transition metal complexes to enhance intersystem-crossing...

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Figure 1. Light absorption by [1] 2+ is followed by photooxidation of [1] 2+ by persulfate, including equations of initial light-driven reactions. The organic chromophore investigated here is a substituted version of perylene diimide (PDI). PDIs are known for their activity as photosensitizers in photoredox catalysis in organic solution and their aggregation behavior in solution. 13-16 Typically, PDIs absorb light in the visible region of the solar spectrum, and therefore enable for low-energy photon emission compared to UV light which might be relevant in the technological context using LED light sources for photochemical reactions. In this study, PDI has been substituted with two butyl trimethyl ammonium alkyl chains at the iminenitrogens, forming N, N'-di(butylenetrimethylammonium)-3,4,9,10-perylenediimide [1] 2+ as PF 6 salt ([1] 2+ , see Figure 1). In principle, the length of the molecule matches the thickness of phospholipid
Figure 2. Synthesis of [1] 2+ starting from perylene-3,4,9,10-tetracarboxylic dianhydride and incorporation of [1] 2+ into vesicle membranes. Reaction conditions and yields: 1.) 4 eq (4-aminobutyl) dimethylamine, i-butanol, 90°C, 24 h, 95 %, 2.a) 3eq., CH 3 I, toluene, reflux, 3h; 2.b) excess NH 4 PF 6 , H 2 O, 65 °C, 76 %. 3.) phosphate buffer, 100:1:1 (n/n/n) DOPG lipids/14:0 PEG2000 PE / [1] 2+ , 4.) extrusion, and 5.) size exclusion chromatography (SEC).
Figure 7. Stern-Volmer quenching experiments for different systems, a) acetonitrile/water 1:1 (V:V), b) DOPG:(14:0 PEG2000 PE):[1] 2+ = 100:1:1 liposomes in phosphate buffer (10 mM, pH 7.0) without size exclusion chromatography, c) DOPG:(14:0 PEG2000 PE):[1] 2+ = 100:1:1 liposomes in phosphate buffer (10 mM, pH 7.0) after size exclusion chromatography.
Alignment and photooxidation dynamics of a perylene diimide chromophore in lipid bilayers

February 2023

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105 Reads

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3 Citations

Molecular Systems Design & Engineering

We present a method of enabling photochemical reactions in water by using biomimetic, water-soluble liposomes and a specifically functionalized perylene diimide chromophore. Linking two flexible saturated C4-alkyl chains with terminal positively charged trimethylammonium groups to the rigid perylene diimide core yielded [1]2+ allowing for its co-assembly at the lipid bilayer interface of DOPG liposomes (DOPG = 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol)) with a preferred orientation and in close proximity to the water interface. According to molecular dynamics simulations the chromophore aligns preferably parallel to the membrane surface which is supported by confocal microscopy. Irradiation experiments with visible light and in the presence of a negatively charged, water-soluble oxidant were slower in the DOPG-membrane than under acetonitrile-water reaction conditions. The generated radical species was characterized by EPR spectroscopy in an acetonitrile-water mixture and associated to the DOPG-membrane. Time-resolved emission studies revealed a static quenching process for the initial electron transfer from photoexcited [1]2+ to the water soluble oxidant. The findings presented in this study yield design principles for the functionalization of lipid bilayer membranes which will be relevant for the molecular engineering of artificial cellular organelles and nano-reactors based on biomimetic vesicles and membranes.


(a) Schematic representation of the synthetic procedures for conventional yellow Y‐CNx and low‐bandgap reddish R‐CNx; diffuse reflectance spectra (b) and corresponding Tauc plots (assuming direct nature of the optical transition) for Y‐CNx (c) and R‐CNx (d).
Corrigendum: A Study in Red: The Overlooked Role of Azo‐Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

September 2022

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50 Reads


Two‐Dimensional Photosensitizer Nanosheets via Low‐Energy Electron Beam Induced Cross‐Linking of Self‐Assembled Ru(II) Polypyridine Monolayers

April 2022

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34 Reads

Angewandte Chemie

Artificial photosynthesis for hydrogen production is an important element in the search for green energy sources. The incorporation of photoactive units into mechanically stable 2D materials paves the way toward the realization of ultrathin membranes as mimics for leaves. Here we present and compare two concepts to introduce a photoactive Ru(II) polypyridine complex into ~1 nm thick carbon nanomembranes (CNMs) generated by low‐energy electron irradiation induced cross‐linking of aromatic self‐assembled monolayers. The photoactive units are either directly incorporated into the CNM scaffold or covalently grafted to its surface. We characterize Ru(II) CNMs using X‐ray photoelectron, surface‐enhanced Raman, photothermal deflection spectroscopy, atomic force, scanning electron microscopy, and study their photoactivity in graphene field‐effect devices. Therewith, we explore the applicability of low‐energy electron irradiation of metal complexes for photosensitizer nanosheet formation.



A Highly Fluorescent Dinuclear Aluminium Complex with Near‐Unity Quantum Yield

February 2022

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97 Reads

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17 Citations

The high natural abundance of aluminium makes the respective fluorophores attractive for various optical applications, but photoluminescence quantum yields above 0.7 have yet not been reported for solutions of aluminium complexes. In this contribution, a dinuclear aluminium(III) complex featuring enhanced photoluminescence properties is described. Its facile one‐pot synthesis originates from a readily available precursor and trimethyl aluminium. In solution, the complex exhibits an unprecedented photoluminescence quantum yield near unity (Φabsolute 1.0±0.1) and an excited‐state lifetime of 2.3 ns. In the solid state, J‐aggregation and aggregation‐caused quenching are noted, but still quantum yields of 0.6 are observed. Embedding the complex in electrospun non‐woven fabrics yields a highly fluorescent fleece possessing a quantum yield of 0.9±0.04.


A Highly Fluorescent Dinuclear Aluminium Complex with Near‐Unity Quantum Yield

February 2022

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33 Reads

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1 Citation

Angewandte Chemie

The high natural abundance of aluminium makes the respective fluorophores attractive for various optical applications, but photoluminescence quantum yields above 0.7 have yet not been reported for solutions of aluminium complexes. In this contribution, a dinuclear aluminium(III) complex featuring enhanced photoluminescence properties is described. Its facile one‐pot synthesis originates from a readily available precursor and trimethyl aluminium. In solution, the complex exhibits an unprecedented photoluminescence quantum yield near unity (Φabsolute 1.0 ± 0.1) and an excited‐state lifetime of 2.3 ns. In the solid state, J‐aggregation and aggregation‐caused quenching are noticed, but still quantum yields of 0.6 are observed. Embedding the complex in electrospun non‐woven fabrics yields a highly fluorescent fleece possessing a quantum yield of 0.9 ± 0.04.


Photoactive ultrathin molecular nanosheets with reversibly lanthanide binding terpyridine centers

December 2021

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44 Reads

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4 Citations

Nanoscale

In recent years, functional molecular nanosheets have attracted much attention in the fields of sensors and energy storage. Here, we present an approach for the synthesis of photoactive metal-organic nanosheets with ultimate molecular thickness. To this end, we apply low-energy electron irradiation induced cross-linking of 4'-(2,2':6',2''-terpyridine-4'-yl)-1,1'-biphenyl-4-thiol self-assembled monolayers on gold to convert them into functional ∼1 nm thick carbon nanomembranes possessing the ability to reversibly complex lanthanide ions (Ln-CNMs). The obtained Ln-CNMs can be prepared on a large-scale (>10 cm2) and inherit the photoactivity of the pristine terpyridine lanthanide complex (Ln(III)-tpy). Moreover, they possess mechanical stability as free-standing sheets over micrometer sized openings. The presented methodology paves a simple and robust way for the preparation of ultrathin nanosheets with tailored photoactive properties for application in photocatalytic and energy conversion devices.


The electron that breaks the catalyst’s back – excited state dynamics in intermediates of molecular photocatalysts

December 2021

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65 Reads

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6 Citations

Physical Chemistry Chemical Physics

In situ spectroelectrochemical studies focussing on the Franck-Condon region and sub-ns electron transfer processes in Ru(II)-tpphz-Pt(II) based photocatalysts reveal that single-electron reduction effectively hinders intramolecular electron transfer between the photoexcited...


Citations (81)


... Another system uses a perylene diamine chromophore that imbeds in liposomal membranes. 168 Use of liposomes as a platform for energy transfer, electron transfer and chemical conversion is a branch of its own within the eld of developing bio-based systems for solar fuel generation. 169,170 Within the context of designing whole-cell systems, the relevance of synthetic membrane components such as these can only be judged by their ability to insert into the biological membranes of microbes and interact with native components. ...

Reference:

Engineering of bespoke photosensitiser–microbe interfaces for enhanced semi-artificial photosynthesis
Alignment and photooxidation dynamics of a perylene diimide chromophore in lipid bilayers

Molecular Systems Design & Engineering

... With these measures of activity, DIB-Ph is well within the range of the highest reported TON for organic PSs. 69 What stands out is the TOF of the reported system, which is only topped by the benchmark molecular noble metal PS [Ru(bpy) 3 ] 2+ . 53 DIB-Ph was further investigated by TDDFT as well as by steady-state and transient absorption spectroscopy in different environments. ...

Not that innocent – ammonium ions boost homogeneous light-driven hydrogen evolution
  • Citing Article
  • March 2022

Chemical Communications

... Previously, this computational protocol was shown to provide an unambiguous description (with respect to the long-range corrected CAM-B3LYP 112 and the B3LYP10 functional�a functional based on B3LYP with 10% exact exchange) of the ground and excited state properties for this class of Al(III) complexes. 1,67 Additionally, scalar-relativistic TDDFT simulations were carried out utilizing Orca 5.0.3 113 with the Douglas−Kroll−Hess (DKH) approach to assess prominent pathways for ISC of Al1, Al2 and Al3 within the previously optimized S 0 structures. Notably, the herein applied DKH method is computationally slightly less demanding than the zeroth-order regular approximation 114 while both methods typically provide comparable accuracies. ...

A Highly Fluorescent Dinuclear Aluminium Complex with Near‐Unity Quantum Yield

... Nevertheless, the number of systematic studies investigating how the electronic structure of the peripheral ligands around the Ru(II) PS influences the structure-property-functionality relationships of respective homogeneous intramolecular PS-B-CAT photocatalysts for photocatalytic hydrogen production remain limited in the literature. [19,[23][24][25] Among the few examples available, Ru-B-Pt photocatalysts, incorporating tetrapyrido[3,2-a : 2',3'-c : 3",2"-h : 2"',3"'-j]phenazine (tpphz), [17,26] 2,2' : 5',2"-terpyridine (tpy), [23,24] or amide linked bi-(pyridines)/ phenanthroline briging ligands (B) [4,27] and 2,2'-bipyridine (bpy) type peripheral ligands (L) on the PS, have been explored and are depicted in Figure 1. The electronic properties of the bpy ligands have been modulated by introducing substituents, such as tert-butyl-(tbbpy), [17] carboxyethyl-(dceb), [23,24] or trifluoromethyl groups-(fbpy) [26] at the 4,4'-position of bpy. ...

The electron that breaks the catalyst’s back – excited state dynamics in intermediates of molecular photocatalysts
  • Citing Article
  • December 2021

Physical Chemistry Chemical Physics

... 41 The binding energy (BE) of the Pt 4f spectrum matches the oxidation state of Pt(II), and the detected N 1s signal is shifted toward a higher BE of 400.1 eV in comparison to typical pyridinic nitrogen spectra (399.0 eV) (Figure 2b), which is typical for the formation of metal complexes with (bi)pyridine-based ligands. 42,43 The Pd 3d spectrum shows a single doublet at a BE corresponding to the oxidation state of Pd(II) (Figure 2c). 44 Similar to P-Pt, the N 1s spectrum of P-Pd is shifted to higher BE (399.7 eV) ( Figure 2d). ...

Photoactive ultrathin molecular nanosheets with reversibly lanthanide binding terpyridine centers
  • Citing Article
  • December 2021

Nanoscale

... [9][10][11][12][13][14] Taking critical lessons from enzyme active sites, a large amount of research on synthetic catalysts has focused on designing ligands that mimic natural systems. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] In this review, species that utilize sustainable first-row transition metals for HER will be the main focus. [33] An overview of fundamental ligand design principles will be presented first, and then recent efforts to translate the successes seen with homogeneous HER catalysts to supported molecular systems will be highlighted and discussed. ...

Hydrogen Production at a NiO Photocathode Based on a Ruthenium Dye–Cobalt Diimine Dioxime Catalyst Assembly: Insights from Advanced Spectroscopy and Post-operando Characterization
  • Citing Article
  • October 2021

ACS Applied Materials & Interfaces

... We could afterward successfully demonstrate sulfide to sulfone oxidation in the presence of hydrogen peroxide as an oxidant [14], as well as light-driven HER using cationic [Ru(bpy) 3 ] 2+ photosensitizer (PS) electrostatically attached to the [Mo 3 S 13 ] 2− layer [15]. Further, we also demonstrated the successful covalent attachment of the Ru-based PS to the membrane made of poly(styrene-co-isoprene)-block-poly((4-vinylbenzyl chloride)-co-(tri(ethylene glycol) methyl ester acrylate)) (P(S-co-I)-b-P(VBCl-co-TEGA)) [16]. In our latest work, we successfully applied the PS-b-PDMAEMA membrane modified with electrostatically attached [Ru(bpy) 3 ] 2+ PS and polyoxometalate cluster [Co 4 (H 2 O) 2 -(PW 9 O 34 ) 2 ] 10− catalyst (POW-WOC) for water oxidation catalysis [17]. ...

A Molecular Photosensitizer in a Porous Block Copolymer Matrix‐Implications for the Design of Photocatalytically Active Membranes

... By now, there are still a few cases of heteroleptic diimine-diphosphine copper(I) complexes showing an absorption at longer wavelengths than 450 nm. [20][21][22][23][24][25] In this work, we aimed at new heteroleptic Cu(I) complexes of type (NN)Cu(PP) with a broad and intense absorption in the visible range. We used bis[(2diphenylphosphino) phenyl] ether (DPEPhos) as chelating diphosphine and as diimine ligands, 4-(benzo[g]quinoxal-2'-yl)-1,2,3triazole-derivatives. ...

Modulating the Excited-State Decay Pathways of Cu(I) 4 H -Imidazolate Complexes by Excitation Wavelength and Ligand Backbone
  • Citing Article
  • October 2021

The Journal of Physical Chemistry B

... Polymeric carbon nitrides (PCN) are sustainable, tunable, non-toxic and chemically stable materials [1][2][3][4], that have been utilized in the construction of various photocatalytic systems for a wide range of light-driven reactions, including hydrogen evolution [5][6][7][8][9][10], water oxidation [6,11,12], CO 2 reduction [13,14], organic pollutant degradation [15][16][17], or selective chemical conversions [18][19][20][21]. Notably, a vast majority of the studies on PCN-based photocatalytic systems encompassed investigations of suspensions of PCN powders, whereas studies of photoelectrocatalytic systems utilizing PCN-based photoelectrodes are much less frequent. ...

A Study in Red: The Overlooked Role of Azo‐Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

... [11] The catalytic efficiency of the lightdriven hydrogen evolution reaction of RuPtI 2 and the related RuPdCl 2 is strongly dependent on several factors such as the nature of the sacrificial electron donor [12] and supramolecular aggregation phenomena. [13][14][15] The interaction with polyaromatic supramolecular activators via p-p bonding with the bridging ligand led to a reduction in the induction phase and an improved initial turnover frequency (TOF) and turnover number (TON) for RuPdCl 2 . [13] The nature of the applied solvent mixtures has a profound effect on the attainable catalytic activity. ...

Switching the Mechanism of NADH Photooxidation by Supramolecular Interactions