An unprecedented method of producing molecular radical cations of oligopeptides in the gas phase has been discovered. Electrospraying a methanolic mixture of a Cu(II)-amine complex, e.g., Cu II (dien)(NO 3 ) 2 (where dien ) diethylenetriamine), and an oligopeptide (M) yields the [Cu II (dien)M] •2+ ion, whose collision-induced dissociation (CID) produces [Cu I (dien)] + and M •+ , the molecular cation of the oligopeptide. Abundant M •+ is apparent when the oligopeptide contains both a tyrosyl and a basic residuesarginyl, lysyl, or histidyl. These structural requirements are similar to those in the metalloradical enzyme process in photosystem II. Tandem mass spectrometry of M •+ produces fragment ions that are both common to and also different from [M + H] + . The fragmentation chemistry of M •+ and of its products appear to be radical driven.Protein radicals have generated a lot of recent interest because of their unusual role in catalyzing a number of important reactions, 1 including the oxidation of water to oxygen for use in a photosynthesis system in plants and algae. 1a,b A common theme in these protein radicals is that they are synthesized posttranslationally and their formation involves metallo cofactors located either adjacent to the amino acid residue being oxidized or on a second subunit or activating enzyme that participates in the oxidation. 1 Frequent radical sites are located on the glycyl, tyrosyl, and tryptophanyl residues; the structure of the glycyl radical in pyruvate formate lyase has been found to be planar and maintain a gas-phase-like structure, despite being embedded in the protein. 1d Here we report results of a serendipitous discovery of an unprecedented route for generating molecular radical cations of oligopeptides in the gas phase. Some of the conditions under which these oligopeptide radical cations are generated bear a resemblance to those in vivo for protein radicals. It is noteworthy that this discovery centers on molecular radical cations as opposed to the more frequently encountered radical ions produced from protonated peptides capturing an electron 2 and metal-bearing peptide ternary complexes. 3 Although electron ionization (EI) is the most widely used method in mass spectrometry to generate radical cations, it is not amenable to oligopeptides because of their low volatility. Very few dipeptides and, as far as we know, only one tripeptide have been successfully ionized in this manner; their mass spectra were rich and contained a wealth of sequencing information. 4 We are reporting herein that electrospraying a methanolic mixture of a Cu(II)-amine complex, e.g., Cu II (dien)(NO 3 ) 2 (where dien ) diethylenetriamine), and an oligopeptide (M) yields the [Cu II -(dien)M] •2+ ion, whose collision-induced dissociation (CID) produces [Cu I (dien)] + and M •+ , the odd-electron (OE) molecular cation of the oligopeptide. Abundant M •+ is apparent only when the oligopeptide contains a tyrosyl and a basic residuesarginyl, lysyl, or histidyl. Figure 1 shows the product ion spectra of...

Achieving visible-light-driven carbon dioxide reduction with high selectivity control and durability while using only earth abundant elements requires new strategies. Hybrid catalytic material was prepared upon covalent grafting a Co−quaterpyridine molecular complex to semiconductive mesoporous graphitic carbon nitride (mpg-C 3 N 4) through an amide linkage. The molecular material was characterized by various spectroscopic techniques, including XPS, IR, and impedance spectroscopy. It proved to be a selective catalyst for CO production in acetonitrile using a solar simulator with a high 98% selectivity, while being remarkably robust since no degradation was observed after 4 days of irradiation (ca. 500 catalytic cycles). This unique combination of a selective molecular catalyst with a simple and robust semiconductive material opens new pathways for CO 2 catalytic light-driven reduction.

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