Highly Active Yttrium Catalysts for the Ring-Opening Polymerization of ε‑Caprolactone and δ‑Valerolactone

The activity of several yttrium alkoxide and aryloxide complexes supported by a ferrocene-based ligand incorporating two thiol phenolates, thiolfan (1,1′-bis­(2,4-di-<i>tert</i>-butyl-6-thiomethylenephenoxy)­ferrocene), was studied. The <i>tert</i>-butoxide complex could only be isolated in the ate form, while a monophenoxide complex could be obtained for OAr = 2,6-di-<i>tert</i>-butylphenolate. The synthetic utility of these yttrium complexes has been demonstrated by the ring-opening polymerization of cyclic esters, with a high activity toward ε-caprolactone and δ-valerolactone being found for the yttrium phenoxide complex

Highly Active Yttrium Catalysts for the Ring-Opening Polymerization of ε‑Caprolactone and δ‑Valerolactone

The activity of several yttrium alkoxide and aryloxide complexes supported by a ferrocene-based ligand incorporating two thiol phenolates, thiolfan (1,1′-bis­(2,4-di-<i>tert</i>-butyl-6-thiomethylenephenoxy)­ferrocene), was studied. The <i>tert</i>-butoxide complex could only be isolated in the ate form, while a monophenoxide complex could be obtained for OAr = 2,6-di-<i>tert</i>-butylphenolate. The synthetic utility of these yttrium complexes has been demonstrated by the ring-opening polymerization of cyclic esters, with a high activity toward ε-caprolactone and δ-valerolactone being found for the yttrium phenoxide complex

Pursuit of Record Breaking Energy Barriers: A Study of Magnetic Axiality in Diamide Ligated Dy^III Single-Molecule Magnets

Dy^III single-ion magnets (SIMs) with strong axial donors and weak equatorial ligands are attractive model systems with which to harness the maximum magnetic anisotropy of Dy^III ions. Utilizing a rigid ferrocene diamide ligand (NN^TBS), a Dy^III SIM, (NN^TBS)­DyI­(THF)₂, <b>1-Dy</b> (NN^TBS = fc­(NHSi<i>t</i>BuMe₂)₂, fc = 1,1′-ferrocenediyl), composed of a near linear arrangement of donor atoms, exhibits a large energy barrier to spin reversal (770.8 K) and magnetic blocking (14 K). The effects of the transverse ligands on the magnetic and electronic structure of <b>1-Dy</b> were investigated through <i>ab initio</i> methods, eliciting significant magnetic axiality, even in the fourth Kramers doublet, thus demonstrating the potential of rigid diamide ligands in the design of new SIMs with defined magnetic axiality

Pursuit of Record Breaking Energy Barriers: A Study of Magnetic Axiality in Diamide Ligated Dy^III Single-Molecule Magnets

Dy^III single-ion magnets (SIMs) with strong axial donors and weak equatorial ligands are attractive model systems with which to harness the maximum magnetic anisotropy of Dy^III ions. Utilizing a rigid ferrocene diamide ligand (NN^TBS), a Dy^III SIM, (NN^TBS)­DyI­(THF)₂, <b>1-Dy</b> (NN^TBS = fc­(NHSi<i>t</i>BuMe₂)₂, fc = 1,1′-ferrocenediyl), composed of a near linear arrangement of donor atoms, exhibits a large energy barrier to spin reversal (770.8 K) and magnetic blocking (14 K). The effects of the transverse ligands on the magnetic and electronic structure of <b>1-Dy</b> were investigated through <i>ab initio</i> methods, eliciting significant magnetic axiality, even in the fourth Kramers doublet, thus demonstrating the potential of rigid diamide ligands in the design of new SIMs with defined magnetic axiality

Intramolecular Crossed [2+2] Photocycloaddition through Visible Light-Induced Energy Transfer

Herein, we present the intramolecular [2+2] cycloadditions of dienones promoted through sensitization, using a polypyridyl iridium­(III) catalyst, to form bridged cyclobutanes. In contrast to previous examples of straight [2+2] cycloadditions, these efficient crossed additions were achieved under irradiation with visible light. The reactions delivered desired bridged benzobicycloheptanone products with excellent regioselectivity in high yields (up to 96%). This process is superior to previous syntheses of benzobicyclo[3.1.1]­heptanones, which are readily converted to B-norbenzomorphan analogues of biological significance. Electrochemical, computational, and spectroscopic studies substantiated the mechanism of triplet energy transfer and explained the unusual regiocontrol

Synthesis of <i>N</i> = 8 Armchair Graphene Nanoribbons from Four Distinct Polydiacetylenes

We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes (PDAs <b>1</b> and <b>2a–c</b>) into virtually indistinguishable <i>N</i> = 8 armchair graphene nanoribbons ([8]_AGNR). PDAs <b>1</b> and <b>2a–c</b> are themselves easily accessed through photochemically initiated topochemical polymerization of diynes <b>3</b> and <b>4a–c</b> in the crystal. The clean, quantitative transformation of PDAs <b>1</b> and <b>2a–c</b> into [8]_AGNR occurs via a series of Hopf pericyclic reactions, followed by aromatization reactions of the annulated polycyclic aromatic intermediates, as well as homolytic bond fragmentation of the edge functional groups upon heating up to 600 °C under an inert atmosphere. We characterize the different steps of both processes using complementary spectroscopic techniques (CP/MAS ¹³C NMR, Raman, FT-IR, and XPS) and high-resolution transmission electron microscopy (HRTEM). This novel approach to GNRs exploits the power of crystal engineering and solid-state reactions by targeting very large organic structures through programmed chemical transformations. It also affords the first reported [8]_AGNR, which can now be synthesized on a large scale via two operationally simple and discrete solid-state processes

Synthesis of <i>N</i> = 8 Armchair Graphene Nanoribbons from Four Distinct Polydiacetylenes

We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes (PDAs <b>1</b> and <b>2a–c</b>) into virtually indistinguishable <i>N</i> = 8 armchair graphene nanoribbons ([8]_AGNR). PDAs <b>1</b> and <b>2a–c</b> are themselves easily accessed through photochemically initiated topochemical polymerization of diynes <b>3</b> and <b>4a–c</b> in the crystal. The clean, quantitative transformation of PDAs <b>1</b> and <b>2a–c</b> into [8]_AGNR occurs via a series of Hopf pericyclic reactions, followed by aromatization reactions of the annulated polycyclic aromatic intermediates, as well as homolytic bond fragmentation of the edge functional groups upon heating up to 600 °C under an inert atmosphere. We characterize the different steps of both processes using complementary spectroscopic techniques (CP/MAS ¹³C NMR, Raman, FT-IR, and XPS) and high-resolution transmission electron microscopy (HRTEM). This novel approach to GNRs exploits the power of crystal engineering and solid-state reactions by targeting very large organic structures through programmed chemical transformations. It also affords the first reported [8]_AGNR, which can now be synthesized on a large scale via two operationally simple and discrete solid-state processes

Synthesis of <i>N</i> = 8 Armchair Graphene Nanoribbons from Four Distinct Polydiacetylenes

We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes (PDAs <b>1</b> and <b>2a–c</b>) into virtually indistinguishable <i>N</i> = 8 armchair graphene nanoribbons ([8]_AGNR). PDAs <b>1</b> and <b>2a–c</b> are themselves easily accessed through photochemically initiated topochemical polymerization of diynes <b>3</b> and <b>4a–c</b> in the crystal. The clean, quantitative transformation of PDAs <b>1</b> and <b>2a–c</b> into [8]_AGNR occurs via a series of Hopf pericyclic reactions, followed by aromatization reactions of the annulated polycyclic aromatic intermediates, as well as homolytic bond fragmentation of the edge functional groups upon heating up to 600 °C under an inert atmosphere. We characterize the different steps of both processes using complementary spectroscopic techniques (CP/MAS ¹³C NMR, Raman, FT-IR, and XPS) and high-resolution transmission electron microscopy (HRTEM). This novel approach to GNRs exploits the power of crystal engineering and solid-state reactions by targeting very large organic structures through programmed chemical transformations. It also affords the first reported [8]_AGNR, which can now be synthesized on a large scale via two operationally simple and discrete solid-state processes

Synthesis of <i>N</i> = 8 Armchair Graphene Nanoribbons from Four Distinct Polydiacetylenes

We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes (PDAs <b>1</b> and <b>2a–c</b>) into virtually indistinguishable <i>N</i> = 8 armchair graphene nanoribbons ([8]_AGNR). PDAs <b>1</b> and <b>2a–c</b> are themselves easily accessed through photochemically initiated topochemical polymerization of diynes <b>3</b> and <b>4a–c</b> in the crystal. The clean, quantitative transformation of PDAs <b>1</b> and <b>2a–c</b> into [8]_AGNR occurs via a series of Hopf pericyclic reactions, followed by aromatization reactions of the annulated polycyclic aromatic intermediates, as well as homolytic bond fragmentation of the edge functional groups upon heating up to 600 °C under an inert atmosphere. We characterize the different steps of both processes using complementary spectroscopic techniques (CP/MAS ¹³C NMR, Raman, FT-IR, and XPS) and high-resolution transmission electron microscopy (HRTEM). This novel approach to GNRs exploits the power of crystal engineering and solid-state reactions by targeting very large organic structures through programmed chemical transformations. It also affords the first reported [8]_AGNR, which can now be synthesized on a large scale via two operationally simple and discrete solid-state processes