Selected scientific achievements (by him and his Group) are illustrated and briefly summarized (2 pages) as follows, within main research lines.
- Catalysis towards
Alkane Functionalization under mild conditions for the single-pot syntheses of added value organic compounds (e.g., alcohols, ketones, carboxylic acids, esters or organo-halides).
Ex1: The most active catalytic systems for oxidative carboxylation of alkanes (including methane and ethane) to carboxylic acids were developed. They are based on Amavadin (a natural non-oxido vanadium complex present in amanita toadstools) and its models. The solvent trifluoroacetic acid (TFA) behaves as the carbonylating agent, apart from CO, and new types of radical mechanisms were disclosed. Much simpler and sustainable process for carboxylic acids than the industrial ones.
Ex2: The first alkane hydrocarboxylation system (water as the hydroxylating agent) was achieved. It is a development of the above system, operating in water-acetonitrile medium instead of TFA, at ambient temperature. Works under metal-free conditions, but with improved performance by suitable metal catalysts. Replacement of acetonitrile by an ionic liquid shows advantages towards sustainability.
Ex3: The first multi-copper catalysts, inspired on particulate methane monooxygenase (pMMO), for the peroxidative oxidation of alkanes to alcohols and ketones. Operate in partially aqueous medium. Water soluble heterometallic complexes and MOFs based on Cu, Fe and other metals as highly active catalysts under mild conditions with aqueous H2O2 as oxidant.
Ex4: Non-transition metal catalytic systems for alkane oxidations with aqueous H2O2. Theoretical studies applied to predict reactivity to diverse metals(III) of groups 13 and 15 (also of related group 3), subsequently proved by experimental studies. Novel types of mechanisms based on such metals, where the metal oxidation state is preserved and the hydroperoxide ligand is redox active (metal-ligand cooperation).
Ex5: Direct partial oxidation (with ozone) of cyclohexane to adipic acid (material for Nylon) catalyzed by an Fe scorpion catalyst, in a solvent-free, radiation-free, heating-free, N2O-free (HNO3-free) process, much simpler and much more sustainable than the industrial processes.
Ex6: Catalysis under unconventional conditions, namely in ionic liquids, supercritical CO2, assisted by microwaves.
Ex7: (Direct) self-assembly synthesis of mono- and multinuclear homo- and heterometallic complexes and coordination polymers (MOFs) as catalysts for the above alkane peroxidative oxidation and hydrocarboxylation in partially aqueous media, as well as for other types of catalytic reactions, e.g., Bayer-Villiger oxidation of ketones and Henry (nitroaldol) C-C couplings in water.
Ex8: Synthesis of water soluble complexes (with hydrosolule scorpionates, amino-polyalcohols, benzene-polycarboxylates, N-hydroxyiminodicarboxylates, azo derivatives of b-diketones, etc) and their application in catalysis in aqueous media, namely in alkane functionalization.
Water Oxidation to dioxygen: The first water oxidation catalytic system based on a molecular catalyst of an early transition metal (up to group 7), also the first one based on a metallobiomolecule (Amavadin), which, moreover, operates in the dark, with Ce(IV) as oxidant. A novel type of mechanism based on a single metal and on a metal-ligand cooperation was disclosed, taking advantage of the redox activity of the ligand oxyiminate moiety.
- Metal-mediated Synthesis
Of a variety of organo-nitrogen compounds (e.g., oxadiazolines, oxadiazoles, carboxamides, acetylamides, imidoylamidines, iminoisoindolinones, phthalimides, phthalocyanines, cyano-olefins or tetrazoles), based on the activation, by electron-poor metal centres, of organonitriles towards [2+3]-cycloaddition reactions and nucleoplilic attack by a variety of nucleophiles, namely oximes, nitrones and related ones. Mechanisms established by theoretical studies.
Ex1: An unprecedented and convenient route to phthalocyanines and their complexes based on double addition of oximes to phthalonitriles.
Ex2: Nitrile hydrolysis to carboxamides with a Zn/oxime system under mild conditions, by cooperative metal- and organo-catalysis involving metal-based and oxime-based catalytic cycles.
- Non-covalent Chemistry in Synthesis
Including reactions promoted by Resonance Assisted Hydrogen-bond (RAHB), pi-pi interactions, tetrel interactions, e.g., E/Z isomerizations, activation to nucleophilic attack, liberation of ligands and aldehydes cyanosilylation, in arylhydrazone copper or cobalt complexes.
- Molecular Electrochemistry
Towards establishment of redox potential-structure relationships, applications in electrosynthesis, electrocatalysis and in the induction of chemical reactivity by electron-transfer (ET). Mechanisms were established by digital simulation of fast cyclic voltammetry.
Ex1: Extension to a diversity of types of metal centres and ligands (e.g., to half-sandwich benzene and scorpionate complexes) of redox potential-structure relationship models of Lever and Pickett.
Ex2: The first electrocatalytic system with a Michaelis-Menten type mechanism. Amavadin acts as an ET-mediator in the electrocatalytic oxidation of thiols in water, behaving as an enzyme.
Ex3: ET chain catalytic isomerisation of Re-carbonyl phosphinic complex.
Ex4: ET-induced isomerization of cyanoimido and nitrile Re phosphinic complexes, and ligand effects (single and double square type ECEC mechanisms, where C and E are electrochemical and chemical steps, respectively).
Ex5: ET-induced proton transfer reactions in hydride-Fe and aminocarbyne-Re phosphinic complexes (square type ECEC mechanisms).
- Theoretical Studies
Applied to interpretation and establishment of mechanisms of some of the above reactions, including the alkane functionalizations, namely to understand the promoting role of water as a catalyst for proton-transfer steps, as an amphoteric reagent and as a TS stabilizer, to design catalysts and predict catalytic behaviours (for examples, see above).
- Activation of small unsaturated molecules (such as, isocyanides, nitriles, cyanamides, alkynes, phosphaalkynes, nitric oxide) by electron-rich phosphinic transition metal centres (of Re, Mo, W and Fe), namely to electrophilic attack. Unprecedented routes to multiple metal-carbon (aminocarbynes, phosphidocarbenes), multiple metal-nitrogen (azavinylidenes) and metal-phosphorus (e.g., phosphinidene oxide) bonds were achieved.