Metal-organic frameworksc ontaining multiple metals distributed over crystallographically equivalent framework positions (mixed-metal MOFs) represent an interesting class of materials, since the closev icinity of isolated metal centerso ften gives rise to synergistic effects. However,a ppropriate characterization techniques for detailed investigations of these mixed-metal metal-organicf ramework materials, particularlya ddressing the distribution of metalsw ithin the lattice,a re rarely available.T he synthesis of mixed-metal FeCuBTC materials in direct syntheses provedt ob ed ifficult and only at horough characterizationu sing varioust echniques,l ike powder X-ray diffraction, X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy,u nambiguously evidencedt he formationof am ixed-metalF eCuBTC materialw ith HKUST-1s tructure, which containedb imetallic FeÀCu paddlewheels as wella sm onometallic CuÀCu andF e ÀFe units under optimizeds ynthesis conditions. The in-depthc haracterization showedt hat other synthetic procedures led to impurities, whichc ontained the majority of the applied iron and were impossible or difficult to identify using solely standard characterization techniques. Therefore, this studys hows the necessity to characterize mixed-metal MOFs extensively to unambiguously prove the incorporationo fb oth metals at the desiredp ositions. The controlled positioning of metal centers in mixed-metal metal-organicf ramework materials and the thorough characterization thereof is particularly important to derive structure-property or structure-activity correlations.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.Figure 1. Schematic framework structure (a) andthe characteristic paddlewheel unit (b) of amixed-metal FeCuBTCmaterial with HKUST-1 structure.Figure 5. Best fit calculations and experimentally obtained EXAFS spectra(a+ b), Fourier-transformed EXAFS spectra (c + d) and Fourier back-transformed spectra (e + f) of FeCuBTC at the Cu K-edge (a,c,e) and the Fe K-edge (b,d,f).

Cyclobenzoins are stable and shape-persistent macrocycles which offer promise as components of optoelectronic and porous materials. We report three new cyclotetrabenzoins, derived from biphenyl, naphthalene, and tolane skeletons. Their synthesis relied on the N-heterocyclic carbene-catalyzed benzoin condensation. Isolated as their acetic esters, these compounds are characterized by structures similar in shape, but larger in size than the parent cyclotetrabenzoin. Alkyne groups of the tolane-based cyclotetrabenzoin were post-synthetically functionalized with Co2(CO)6 moieties under mild reaction conditions. File list (4) download file view on ChemRxiv 2020_Eisterhold_Cyclotetrabenzoins_OrgLett_Manuscri... (458.39 KiB) download file view on ChemRxiv 2020_Eisterhold_Cyclotetrabenzoins_OrgLett_Supporti... (763.61 KiB) download file view on ChemRxiv Compound_3b.cif (707.46 KiB) download file view on ChemRxiv Compound_3d.cif (368.64 KiB)

Cyclobenzoins are stable and shape-persistent macrocycles which offer promise as components of optoelectronic and porous materials. We report three new cyclotetrabenzoins, derived from biphenyl, naphthalene, and tolane skeletons. Their synthesis relied on the N-heterocyclic carbene-catalyzed benzoin condensation. Isolated as their acetic esters, these compounds are characterized by structures similar in shape, but larger in size than the parent cyclotetrabenzoin. Alkyne groups of the tolane-based cyclotetrabenzoin were post-synthetically functionalized with Co2(CO)6 moieties under mild reaction conditions.<br>