Sense of competence and optimism as resources to promote academic engagement

5th ICEEPSY International Conference on Education & Educational Psychology in Kyrenia Cyprus (Oct 22-25, 2014)/ guest editors: Zafer Bekirogullari, Melis Minas.Peer reviewe

Coordination–driven encapsulation of transition metal complexes in molecular capsules and their application in hydroformylation and proton reduction catalysis

Traditional homogeneous catalysis applies catalysts based on organometallic complexes which are tuned by changing the metal and/or the ligands that are coordinated to it. Catalyst-substrate interactions which dictate the outcome of a reaction occur solely on the metal, i.e. the ‘first coordination sphere’. Catalysts of nature, ‘enzymes’, serve as a source of inspiration due their inherently high activity and selectivity in selected catalytic transformations. The success of enzymes lies in their use of a larger toolbox to steer the outcome of reactions compared to traditional homogeneous catalysts. Confinement of the active site in a bulky second coordination sphere is key, resulting in a local microenvironment radically different from bulk solution. In this thesis, the effect of synthetic second coordination spheres on encapsulated rhodium-based catalysts and bio-inspired hydrogenase mimics is studied. Chapter 2 reports on the encapsulation of a rhodium complex in a supramolecular assembly, resulting in a catalyst that displays unprecedented branched selectivity in the hydroformylation of propene. Chapter 3 discusses the first example of substrate–selective hydroformylation of terminal alkenes by a rhodium catalyst encapsulated in a metal-organic cage. Chapter 4 elaborates on the design of a biomimetic and fully base–metal photocatalytic system for photocatalytic proton reduction. Chapter 5 reports a new tetrahedral porphyrin–based M4L6 cage that selectively encapsulates an iron-iron hydrogenase mimic and thereby decreases its catalytic overpotential by 150 mV. Chapter 6 shows the design and synthesis of a novel supramolecular cage-based functional rotaxane

Synthesis and Characterization of Self‐Assembled Chiral Fe^II₂L₃ Cages

We present here the synthesis of chiral BINOL‐derived (BINOL=1,1′‐bi‐2‐naphthol) bisamine and bispyridine‐aldehyde building blocks that can be used for the self‐assembly of novel chiral FeII2L3 cages when mixed with an iron(II) precursor. The properties of a series of chiral cages were studied by NMR and circular dichroism (CD) spectroscopy, cold‐spray ionization MS, and molecular modeling. Upon formation of the M2L3 cages, the iron corners can adopt various isomeric forms: mer, fac‐Δ, or fac‐Λ. We found that the coordination geometry around the metal centers in R‐Cages 1 and 2 were influenced by the chiral BINOL backbone only to a limited extent, as a mixture of cages was formed with fac and mer configurations at the iron corners. However, single cage species (fac‐ RR‐Cage and fac‐ RS‐Cage ) that are enantiopure and highly symmetric were obtained by generating these chiral M2L3 cages by using the bispyridine‐aldehyde building blocks in combination with chiral amine moieties to form pyridylimine ligands for coordination to iron. Next to consistent NMR spectra, the CD spectra confirm the configurations fac‐(Λ,Λ) and fac‐(Δ,Δ) corresponding to RR‐ and RS‐Cage , respectively

Control of the overpotential of a [FeFe] hydrogenase mimic by a synthetic second coordination sphere

Hydrogen as a renewable fuel is viable when produced sustainably via proton reduction catalysis (PRC). Many homogeneous electrocatalysts perform PRC with high rates, but they all require a large overpotential to drive the reaction. Natural hydrogenase enzymes achieve reversible PRC with potentials close to the thermodynamic equilibrium through confinement of the active site in a well-defined protein pocket. Inspired by nature, we report a strategy that relies on the selective encapsulation of a synthetic hydrogenase mimic in a novel supramolecular cage. Catalyst confinement decreases the PRC overpotential by 150 mV, and is proposed to originate from the cationic cage stabilizing anionic reaction intermediates within the catalytic cycle