Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4
Understanding of interactions among molecules is essential to elucidate the binding of pharmaceuticals on receptors, the mechanism of protein folding and self-assembling of organic molecules. While interactions between two aromatic molecules have been examined extensively, little is known about the interactions between two antiaromatic molecules. Theoretical investigations have predicted that antiaromatic molecules should be stabilized when they stack with each other by attractive intermolecular interactions. Here, we report the synthesis of a cyclophane, in which two antiaromatic porphyrin moieties adopt a stacked face-to-face geometry with a distance shorter than the sum of the van der Waals radii of the atoms involved. The aromaticity in this cyclophane has been examined experimentally and theoretically. This cyclophane exhibits three-dimensional spatial current channels between the two subunits, which corroborates the existence of attractive interactions between two antiaromatic π-systems.
more » « less- Award ID(s):
- 1664674
- NSF-PAR ID:
- 10154009
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract n π electrons. This concept was extended to all‐metal molecules after the observation of Li3Al4−in the gas phase. However, the solid‐phase counterparts have not been documented to date. Herein, we describe a series of all‐metal antiaromatic anions, [Ln(η 4‐Sb4)3]3−(Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single‐crystal X‐ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron‐counting rule, we conclude that the core [Ln(η 4‐Sb4)3]3−fragment of the crystal has three locally π‐antiaromatic Sb4fragments. This complex represents the first locally π‐antiaromatic all‐metal system in the solid state, which is stabilized by interactions of the three π‐antiaromatic units with the central metal atom. -
more » « less
Abstract The self‐assembly in aqueous solution of the well‐known cyclophane, cyclobis(paraquat‐p‐phenylene) (BB4+), and two cucurbit[7]uril (CB7) hosts around a simple hydroquinol‐based, diamine guest (GH22+) was investigated by1H NMR and electronic absorption spectroscopies, electrospray mass spectrometry and DFT computations. The formation of a quaternary supramolecular assembly [GH22+⋅BB4+⋅ (CB7)2] was shown to be a very efficient process, which takes place not only because of the attractive forces between each of the hosts and the guest, but also because of the lateral interactions between the hosts in the final assembly. This complementary set of attractive interactions results in clear cooperative binding effects that help overcome the entropic barriers for multiple component assembly.
-
more » « less
Abstract One route to address climate change is converting carbon dioxide to synthetic carbon‐neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo‐ and heterogeneous catalysis, deoxygenative coupling of CO to products with C−C bonds—as in liquid fuels—remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2
L (2 ), whereL 2−is a bis(β‐diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L ] (3 ), which undergoes silylation to Fe2(CO)(COSiMe3)L (4 ). Subsequent C‐OSiMe3bond cleavage and C=C bond formation occurs upon reduction of4 , yielding Fe2(μ‐CCO)L . CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallestJ value, with changes to local metal ion spin states and coupling schemes (ferro‐ vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of5 with KEt3BH or methanol releases the C2O2−ligand with retention of the diiron core -
more » « less
Abstract One route to address climate change is converting carbon dioxide to synthetic carbon‐neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo‐ and heterogeneous catalysis, deoxygenative coupling of CO to products with C−C bonds—as in liquid fuels—remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2
L (2 ), whereL 2−is a bis(β‐diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L ] (3 ), which undergoes silylation to Fe2(CO)(COSiMe3)L (4 ). Subsequent C‐OSiMe3bond cleavage and C=C bond formation occurs upon reduction of4 , yielding Fe2(μ‐CCO)L . CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallestJ value, with changes to local metal ion spin states and coupling schemes (ferro‐ vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of5 with KEt3BH or methanol releases the C2O2−ligand with retention of the diiron core -
Two-dimensional graphene-like materials, namely MXenes, have been proposed as potential materials for various applications. In this work, the reactivity and selectivity of four MXenes ( i.e. M 2 C (M = Ti, V, Nb, Mo)) and their oxygen-functionalized forms ( i.e. O-MXenes or M 2 CO 2 ) toward gas molecules were investigated by using the plane wave-based Density Functional Theory (DFT) calculations. Small gas molecules, which are commonly found in flue gas streams, are considered herein. Our results demonstrated that MXenes are very reactive. Chemisorption is a predominant process for gas adsorption on MXenes. Simultaneously dissociative adsorption can be observed in most cases. The high reactivity of their non-functionalized surface is attractive for catalytic applications. In contrast, their reactivity is reduced, but the selectivity is improved upon oxygen functionalization. Mo 2 CO 2 and V 2 CO 2 present good selectivity toward NO molecules, while Nb 2 CO 2 and Ti 2 CO 2 show good selectivity toward NH 3 . The electronic charge properties explain the nature of the substrates and also interactions between them and the adsorbed gases. Our results indicated that O-MXenes are potential materials for gas-separation/capture, -storage, -sensing, etc. Furthermore, their structural stability and SO 2 -tolerant nature are attractive properties for using them in a wide range of applications. Our finding provides good information to narrow down the choices of materials to be tested in future experimental work.more » « less
