Bis(benzimidazole)amine‐based copper complexes, with structural similarities to the active sites of Lytic Polysaccharide Monooxygenase enzymes (LPMOs), were tested for the oxidative degradation of cellulose. Spectroscopic characterization of the complexes, as well as structural authentication of one of them, confirm a tetragonal coordination environment with 3 nitrogen donors, as well as a thioether in axial positions. Aqueous oxidative degradation of cellulose was achieved with the CuII complexes and H2O2 as oxidant through putative cupric‐hydroperoxo intermediates. Conversion of cellulose was achieved in up to 67 % yield of soluble oligosaccharide derivatives at ambient temperature and pressure. The products were analyzed in aqueous solution by HPLC‐MS, confirming oxidative depolymerization of cellulose under ambient conditions, in an analogous fashion to LPMOs.

Functionalization of the phenolic rim of p-tert-butylcalix [8]arene with phenanthroline to create a cavity leads to formation of two regioisomers. Substitution of positions 1 and 5 produces the known C 2v -symmetric regioisomer 1,5-(2,9-dimethyl-1,10phenanthroyl)-p-tert-butylcalix[8]arene (L 1,5 ), while substitution of positions 1 and 4 produces the C s -symmetric regioisomer 1,4-(2,9-dimethyl-1,10-phenanthroyl)-p-tert-butylcalix[8]arene (L 1,4 ) described herein. [Cu(L 1,4 )I] was synthesized from L 1,4 and CuI in good yield and characterized spectroscopically. To evaluate the effect of its cavity on catalysis, Ullmann-type CÀ S coupling was chosen as proof-of-concept. Selected aryl halides were used, and the results compared with the previously reported Cu(I)/L 1,5 system. Only highly activated aryl halides generate the CÀ S coupling product in moderate yields with the Cu(I)/L 1,4 system. To shed light on these observations, detailed computational investigations were carried out, revealing the influence of the calix[8]arene macrocyclic morphology on the accessible conformations. The L 1,4 regioisomer undergoes a deformation that does not occur with L 1,5 , resulting in an exposed catalytic center, presumably the cause of the low activity of the former system. The 1,4-connectivity was confirmed in the solid-state structure of the byproduct [Cu(L 1,4 À H)(CH 3 CN) 2 ] that features Cu(I) coordinated inside a cleft defined by the macrocyclic framework.

Five neutral nickel(II) bimetallic models of the active site of [NiFe]-hydrogenase supported by tridentate sulfur-rich RNS 2 ligands, were synthesized and tested as electrocatalysts for proton (H + ) reduction. Complexes were classified according to the À NR substituent (1: 1-methylpyrene; 2: 2-methylthiophene; 3: phenyl) and as type a for those without bulky substituents and type b for the analogues with voluminous groups. Solid state structures were determined for three dimers, revealing [Ni 2 (μ-SAr) 2 ] frameworks, in which the two coordination planes around the Ni centres define a dihedral angle (θ) that is influenced by the substituents on the ligands (2 a:Using CF 3 COOH as H + source, 1 b and 2 b exhibit catalytic activity at À 1.72 V (i cat /i p � 2.40) and À 1.80 V (i cat /i p � 2.89) vs the ferrocenium/ferrocene couple (Fc + / Fc), respectively. In contrast, type a complexes were not viable catalysts. This behaviour suggests a relationship between the dimer conformation and its activity, due to a Ni ••• Ni cooperative effect, which is favoured in angular molecules and appears to assist during electrocatalytic H + reduction.