Guanidinyl‐Functionalized Aromatic Compounds (GFAs) – Charge and Spin Density Studies as Starting Points for the Development of a New Class of Redox‐active Ligands

Himmel, Hans‐Jörg

doi:10.1002/zaac.201200496

Cited by 62 publications

(48 citation statements)

References 80 publications

(61 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Therefore, the small dihedral angles at the copper atoms are not in dissonance with a Cu II complex description. The C=N (imino) bond lengths N1−C7 and N4−C12 increase upon coordination (see Table ), as is typical for guanidine–metal complexes . A structural comparison of the free neutral and oxidized ligands 3/4 and 3 2+ / 4 2+ (Table SI1 in the Supporting Information) with the ligands in the copper complexes [ 3 (CuCl 2 )], [ 4 (CuCl 2 )], and [ 3 (CuBr 2 )] (Table SI3 in the Supporting Information) is also in harmony with a description in terms of Cu II complexes with neutral ligands.…”

Section: Resultssupporting

confidence: 70%

“…Their structures show no peculiarities. The N1−C7/N4−C12 bond lengths (1.295(1)/1.292(1) Å for 3 and 1.293(2)/1.287(2) Å for 4 ) are in line with the imino C=N bond length found in known guanidines . Cyclic voltammetry (CV) experiments show that 3 and 4 are oxidized in solution either in a single reversible two‐electron redox process or in two reversible one‐electron redox processes at different potentials, depending on the applied solvent.…”

Section: Resultssupporting

confidence: 54%

“…Guanidino‐substituted aromatic compounds (GFAs) constitute a relatively new class of redox‐active ligands developed by our group . Examples comprise 1,2,4,5‐tetrakis‐( N , N , N ′, N ′‐tetramethylguanidino)benzene ( 1 , see Scheme c) and 1,4,5,8‐tetrakis‐( N , N , N ′, N ′‐tetramethyl‐guanidino)naphthalene ( 2 ) . All known GFA compounds are thermally stable and can be sublimed without decomposition.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Copper Complexes of New Redox‐Active 4,5‐Bisguanidino‐Substituted Benzodioxole Ligands: Control of the Electronic Structure by Counter‐Ligands, Solvent, and Temperature

Schrempp

Kaifer

Wadepohl

et al. 2016

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Herein, we analyze the possibility of controlling the electronic structure of mononuclear copper complexes featuring new redox-active 4,5-bisguanidino-substituted benzodioxole ligands. The nature of the guanidino groups, the anionic counter-ligands, the applied solvent (polarity), and the temperature are the parameters that decide if a Cu complex with neutral ligand unit or a Cu complex with radical monocationic ligand unit is the adequate description. Under special conditions, a temperature-dependent equilibrium of the two valence tautomeric forms (Cu /neutral ligand and Cu /radical monocationic ligand) is achieved. Removal of a ligand-centered electron from a paramagnetic Cu complex with a neutral ligand unit leads to a diamagnetic Cu complex with a dicationic ligand unit through a redox-induced electron-transfer (RIET) process.

show abstract

Section: Resultssupporting

confidence: 70%

Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Copper Complexes of New Redox‐Active 4,5‐Bisguanidino‐Substituted Benzodioxole Ligands: Control of the Electronic Structure by Counter‐Ligands, Solvent, and Temperature

Schrempp

Kaifer

Wadepohl

et al. 2016

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…Yield: 0.733 g (2.097 mmol, 89%). Elemental analysis for 2·(2,3,6,7-tetraamino-phenazine)·3HCl, C 24 2.…”

Section: Methodsmentioning

confidence: 99%

Tetraguanidino-functionalized phenazine and fluorene dyes: synthesis, optical properties and metal coordination

et al. 2015

Self Cite

View full text Add to dashboard Cite

In this work the first phenazine derivatives with guanidino substituents were prepared and their structural and electronic properties studied in detail. The guanidino groups decrease the HOMO-LUMO gap, massively increase the quantum yield for fluorescence and offer sites for metal coordination. The yellow-orange colored 2,3,7,8-tetraguanidino-substituted phenazine shows intense fluorescence. The wavelength of the fluorescence signal is strongly solvent dependent, covering a region from 515 nm in Et2O solution (with a record quantum yield of 0.39 in Et2O) to 640 nm in water. 2,3-Bisguanidino-substituted phenazine is less fluorescent (maximum quantum yield of 0.17 in THF), but exhibits extremely large Stokes shifts. In contrast, guanidino-functionalized fluorenes emit only very weakly. Subsequently, the influence of coordination on the electronic properties and especially the fluorescence of the phenazine system was analysed. Coordination first takes place at the guanidino groups, and leads to a blue shift of the luminescence signal as well as a massive decrease of the luminescence lifetime. Luminescence is almost quenched completely upon Cu(I) coordination. On the other hand, in the case of Zn(II) coordination the fluorescence signal remains strong (quantum yield of 0.36 in CH3CN). In the case of strong zinc Lewis acids, an excess of metal compound leads to additional coordination at the phenazine N atoms. This is accompanied by significant red-shifts of the lowest-energy transition in the absorption and fluorescence spectra. Pentanuclear complexes with two phenazine units were isolated and structurally characterized, and further aggregation leads to chain polymers.

show abstract

“…Organic compounds of interest in this context include TDAE [tetrakis(dimethylamino)ethylene],3,4 and the tetraaminoethylene derivative 4,5,9,10‐tetrahydro‐3 H ,8 H ‐2a,5a,7a,10a‐tetraazadicyclopenta[ ef , kl ]heptalene shown in Scheme 5. Over the last couple of years, we developed GFAs (guanidinyl‐functionalized aromatic compounds)6 as a new class of organic electron donors and redox‐active ligands with tunable frontier orbital energies 7. Two examples, which are included in Scheme , are 1,2,4,5‐tetrakis(tetramethylguanidinyl)benzene8 and 2,3,5,6‐tetrakis(tetramethylguanidinyl)pyridine 9.…”

Section: Introductionmentioning

confidence: 99%

Urea Azines (Bisguanidines): Electronic Structure, Redox Properties, and Coordination Chemistry

et al. 2015

View full text Add to dashboard Cite

Urea azines are a largely neglected class of compounds. We show herein that they can easily be synthesized and sublimed at higher temperatures (90–100 °C) without decomposition. Our discussion includes the derivatives N,N′‐diisopropylurea azine (2), tetramethylurea azine (3), and N,N′‐dimethylethyleneurea azine (4) as examples. Vibrational spectroscopy and quantum chemical calculations were used to study their electronic structure in detail. A clear trend in the calculated decomposition to N2 and carbene is found, but the analysis reveals that this trend reflects the stability of the carbene decomposition product rather than changes in the electronic structure of the urea azines. Using cyclic voltammetry (CV) measurements we show that the urea azines are strong organic electron donors, which can be oxidized reversibly in two well‐separated one‐electron steps. The radical salt 4(TCNQ), featuring radical monocations and radical monoanions, which form mixed stacks in the solid state, was prepared by reaction of neutral 4 with tetracyanoquinodimethane (TCNQ). Oxidation of 4 with silver salts Ag+X– (X = BF4 or PF6) was accompanied by dehydrogenation, leading to intensively red‐brown colored radical azoimidazolium dyes. Furthermore, urea azines were used as chelating ligands. In the case of 2, coordination to late transition metals initiates tautomerization. Reaction of 2 with boron hydrides leads to hydrogen elimination and formation of new B,N bi‐heterocyclic ring structures.

show abstract

Guanidinyl‐Functionalized Aromatic Compounds (GFAs) – Charge and Spin Density Studies as Starting Points for the Development of a New Class of Redox‐active Ligands

Abstract: This research report is devoted to guanidinyl-functionalized aromatic compounds (GFAs), which represent a new class of strong electron donors and redox-active ligands. Charge and spin density

Cited by 62 publications

References 80 publications

Copper Complexes of New Redox‐Active 4,5‐Bisguanidino‐Substituted Benzodioxole Ligands: Control of the Electronic Structure by Counter‐Ligands, Solvent, and Temperature

Copper Complexes of New Redox‐Active 4,5‐Bisguanidino‐Substituted Benzodioxole Ligands: Control of the Electronic Structure by Counter‐Ligands, Solvent, and Temperature

Tetraguanidino-functionalized phenazine and fluorene dyes: synthesis, optical properties and metal coordination

Urea Azines (Bisguanidines): Electronic Structure, Redox Properties, and Coordination Chemistry

Contact Info

Product

Resources

About