Organic Superstructure Research Articles

Organic superstructure microwires with hierarchical spatial organisation

Rationally designing and precisely constructing the dimensions, configurations and compositions of organic nanomaterials are key issues in material chemistry. Nevertheless, the precise synthesis of organic heterostructure nanomaterials remains challenging owing to the difficulty of manipulating the homogeneous/heterogeneous-nucleation process and the complex epitaxial relationships of combinations of dissimilar materials. Herein, we propose a hierarchical epitaxial-growth approach with the combination of longitudinal and horizontal epitaxial-growth modes for the design and synthesis of a variety of organic superstructure microwires with accurate spatial organisation by regulating the heterogeneous-nucleation crystallisation process. The lattice-matched longitudinal and horizontal epitaxial-growth modes are separately employed to construct the primary organic core/shell and segmented heterostructure microwires. Significantly, these primary organic core/shell and segmented microwires are further applied to construct the core/shell-segmented and segmented-core/shell type’s organic superstructure microwires through the implementation of multiple spatial epitaxial-growth modes. This strategy can be generalised to all organic microwires with tailored multiple substructures, which affords an avenue to manipulate their physical/chemical features for various applications.

Huts and stone arrangements at Hilary Creek, western Queensland: Recent fieldwork at an Australian Aboriginal site complex

This paper reports on an Aboriginal site complex, incorporating hut structures, ceremonial stone arrangements, an extensive surface artefact assemblage of lithics and mussel shell, and a silcrete quarry, located along Hilary Creek, a tributary of the Georgina River in western Queensland, Australia. At least two phases of occupation are indicated. The most recent huts have their collapsed organic superstructure still present, while those of a presumably earlier phase are distinguished as bare, circular patches of earth which are conspicuous amongst the ubiquitous gibber, with or without stone bases, and lacking any collapsed superstructure. Immediately adjacent to the huts and also a few hundred metres away are clusters of small stone arrangements, and about 2 km to the southwest, along the same creekline, is another series of larger, more substantial stone arrangements; these features speak to the importance of the general Hilary Creek area for ceremonial purposes. Radiocarbon dating reveals use of the Hilary Creek complex dates to at least 300 years ago; the absence of any European materials suggests it was likely not used, or only used very sporadically, after the 1870s when pastoralists arrived in the area, and when traditional lifeways were devastated by colonial violence.

Light-driven molecular motion modifying the electronic structure and spin properties of solid organic superstructure

Abstract The polarized light acted as one of the non-contacted media could effectively tune the crystal structure to improve the physical properties. In this work, under polarized laser excitation, the molecular motion is driven inside the crystals, where the electronic structure of the crystal is affected to further change the spin and optical properties. However, decreasing the temperature to 77 K, the external polarized laser cannot produce direct molecular motion. Moreover, switching the incident laser from the linearly to circularly polarized state, the dependence of the molecular motion on the spin and optical properties show pronounced difference.

The geometric and electronic structure of TCNQ and TCNQ+Mn on Ag(0 0 1) and Cu(0 0 1) surfaces

Copper and silver surfaces can be used as model systems to study structure formation and interfacial bonding upon adsorption of organic molecules. We have investigated the geometric and electronic structure of ordered monolayers of TCNQ on Cu(001) and Ag(001) and of TCNQ+Mn on Ag(001) surfaces by LEED and photoelectron momentum microscopy. While TCNQ forms an incommensurable superstructure on Cu(001), two coverage-dependant, commensurable superstructures are established on Ag(001). Subsequent adsorption of Mn on top of TCNQ/Ag(001) results in the formation of a long-range ordered mixed metal–organic superstructure, which is also commensurable with the Ag(001) substrate. The photoelectron spectroscopy (PES) data shows a filling of the TCNQ LUMO by charge transfer from the substrate for all investigated interfaces and the coadsorption of Mn leads to an energy shift of the TCNQ HOMO and LUMO of 230meV with respect to TCNQ/Ag(001). The characteristic angle-dependent intensity pattern of the TCNQ LUMO in PES was utilized to investigate the azimuthal orientation of the molecules in the respective unit cells. The angle-resolved PES data was further analyzed to identify lateral band dispersion effects in the adsorbate layers, but no significant dispersion was observed.

On the Chemistry and Evolution of the Pioneer Organism

The theory of a chemo-autotrophic origin of life in a volcanic Iron-Sulfur World postulates the emergence of a pioneer organism within a flow of volcanic exhalations. The pioneer organism is characterized by a composite structure with an inorganic substructure and an organic superstructure. Within the surfaces of the inorganic substructure, iron, cobalt, nickel, and other transition-metal centers with sulfido, carbonyl, cyano, and other ligands are catalytically active, and promote the growth of the organic superstructure through carbon fixation, driven by the reducing potential of the volcanic exhalations. This pioneer organism is reproductive by an autocatalytic feedback effect, whereby some organic products serve as ligands for activating the catalytic metal centres whence they arise. This unitary structure-function relationship of the pioneer organism constitutes the 'Anlage' for two major strands of evolution: enzymatization and cellularization, whereby the upward evolution of life by increase of molecular complexity is grounded ultimately in the transition metal-catalyzed, synthetic redox chemistry of the pioneer organism.

From volcanic origins of chemoautotrophic life to Bacteria, Archaea and Eukarya.

The theory of a chemoautotrophic origin of life in a volcanic iron-sulphur world postulates a pioneer organism at sites of reducing volcanic exhalations. The pioneer organism is characterized by a composite structure with an inorganic substructure and an organic superstructure. Within the surfaces of the inorganic substructure iron, cobalt, nickel and other transition metal centres with sulphido, carbonyl and other ligands were catalytically active and promoted the growth of the organic superstructure through carbon fixation, driven by the reducing potential of the volcanic exhalations. This pioneer metabolism was reproductive by an autocatalytic feedback mechanism. Some organic products served as ligands for activating catalytic metal centres whence they arose. The unitary structure-function relationship of the pioneer organism later gave rise to two major strands of evolution: cellularization and emergence of the genetic machinery. This early phase of evolution ended with segregation of the domains Bacteria, Archaea and Eukarya from a rapidly evolving population of pre-cells. Thus, life started with an initial, direct, deterministic chemical mechanism of evolution giving rise to a later, indirect, stochastic, genetic mechanism of evolution and the upward evolution of life by increase of complexity is grounded ultimately in the synthetic redox chemistry of the pioneer organism.

Multinuclear ( 13C, 17O, 57Fe) NMR studies of carbonmonoxy heme proteins and synthetic model compounds

13C, 17O and 57Fe NMR spectra of several carbonmonoxy hemoprotein models with varying polar and steric effects of the distal organic superstructure, constraints of the proximal side, and porphyrin ruffling are reported. Both heme models and heme proteins obey a similar excellent linear δ( 13C) versus ν(C–O) relationship which is primarily due to modulation of π-back-bonding from the Fe d π to CO π * orbital by the distal pocket polar interactions. The lack of correlation between δ( 13C) and δ( 17O) suggests that the two probes do not reflect a similar type of electronic and structural perturbation. δ( 17O) is not primarily influenced by the local distal field interactions and does not correlate with any single structural property of the Fe–C–O unit; however, atropisomerism and deformation of the porphyrin geometry appear to play a significant role. 57Fe shieldings vary by nearly 900 ppm among various hemes and an excellent correlation was found between δ( 57Fe) and the absolute crystallographic average displacement of the meso carbon atoms, | C m|, relative to the porphyrin core mean plane. The excellent correlation between iron-57 shieldings and the average shieldings of the meso carbons of the porphyrin skeleton of TPP derivatives suggests that the two probes reflect a similar type of electronic and structural perturbation which is primarily porphyrin ruffling.

Carbon-13 and Oxygen-17 Chemical Shifts, (16O/18O) Isotope Effects on13C Chemical Shifts, and Vibrational Frequencies of Carbon Monoxide in Various Solvents and of the Fe−C−O Unit in Carbonmonoxy Heme Proteins and Synthetic Model Compounds

13C shieldings, δ(13C), 17O shieldings, δ(17O), and 18O isotope effects on 13C shieldings, 1Δ13C(18O/16O), of carbon monoxide (99.7% 13C, 0.9% 17O, and 11.8% 18O enriched) in a variety of solvents and of the Fe−C−O unit of several carbonmonoxy hemoprotein models with varying polar and steric effects of the distal organic superstructure and constraints of the proximal side are reported. This enables, first, comparisons with hemoproteins, C−O vibrational frequencies, ν(C−O), and X-ray structural data to be made; second, to investigate whether polarizable CO is an adequate model for distal ligand effects in carbonmonoxy heme proteins and synthetic model compounds; third, to investigate the effect of electronic perturbation within the heme pocket and pocket deformation on δ(13C), δ(17O), 1Δ13C(18O/16O), and ν(C−O). A variety of solvents with varying dielectric constants and solvation abilities appears to have negligible effect on δ(17O), δ(13C), and 1Δ13C(18O/16O) and little direct effect on ν(C−O) of dissolv...

Iron-57 Nuclear Shieldings as a Quantitative Tool for Estimating Porphyrin Ruffling in Hexacoordinated Carbonmonoxy Heme Model Compounds in Solution

57Fe NMR spectra of several carbonmonoxy hemoprotein models with varying polar and steric effects of the distal organic superstructure, constraints of the proximal side, and porphyrin ruffling are reported. 57Fe shieldings, δ(57Fe), vary by nearly 900 ppm among various hemes, and an excellent correlation was found between δ(57Fe) and the absolute crystallographic average displacement of the meso carbon atoms, |Cm|, relative to the porphyrin core mean plane. The great variation of δ(57Fe) as a function of |Cm| (∼140 ppm/0.1 A) demonstrates that iron-57 shieldings can be used in structure refinement protocols for the extraction of more accurate structures for heme rings in heme model compounds. The excellent correlation between iron-57 shieldings and the average shieldings of the meso carbons of the porphyrin skeleton of TPP derivatives suggests that the two probes reflect similar types of electronic and structural perturbations, which are primarily due to porphyrin ruffling. The present findings also empha...

13C shieldings, 18O isotope effects on 13C shieldings, and 57Fe-13C spin couplings of the Fe-C-O unit in superstructured hemoprotein models: Comparison with hemoproteins, C-O vibrational frequencies, and X-ray structural data

13C NMR spectra of several carbon monoxide (99.7% 13C and 11.8% 18O enriched) hemoprotein models with varying polar and steric effects of the distal organic superstructure and constraints of the proximal side are reported. This enables the 57Fe-13C(O) coupling constants (\(^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }\)), 13C shieldings (δ(13C)), and 18O isotope effects on13 C shieldings (1Δ13C(18O/16O)) to be measured and hence comparisons with hemoproteins, C-O vibrational frequencies and X-ray structural data to be made. Negative polar interactions in the binding pocket and inhibition of Fe/→/CO back-donation or positive distal polar interactions with amide NH groups appear to have little direct effect on \(^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }\) couplings. Similarly, the axial hindered base 1,2-dimethylimidazole has a minor effect on the \(^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }\) values despite higher rates of CO desorption being observed for such complexes. On the contrary,13 C shieldings vary widely and an excellent correlation was found between the infrared C-O vibrational frequencies (ν(C-O)) and13 C shieldings and a reasonable correlation with18 O isotope effects on 13C shieldings. This suggests that δ(13C), ν(C-O) and1 Δ13 C(18O/16O) are accurate monitors of the multiple mechanisms by which steric and electronic interactions are released in superstructured heme model compounds. The 13C shieldings of heme models cover a 4.0 ppm range which is extended to 7.0 ppm when several HbCO and MbCO species at different pH values are included. The latter were found to obey a similar linear δ(13 (13C) versus ν(C-O) relationship, which proves that both heme models and heme proteins are homogeneous from the structural and electronic viewpoint. Our results suggest that ν(C-O), δ(13C) and 1Δ13C(18O/16O) measurements reflect similar interaction which is primarily the modulation of π back-bonding from the Fe dπ to the CO π* orbital by the distal pocket polar interactions. The lack of correlation between1 Δ13 C(18O/16O) and crystallographic CO bond lengths (r(C-O)) reflects significant uncertainties in the X-ray determination of the carbon and oxygen positions.

Design of organic superstructure based on a preorganised donor–acceptor unit

Use of preorganised donor-acceptor molecules for controlling and generating solid-state architecture is demonstrated by a molecule having donors and acceptors nearly orthogonal to each other which yields a superstructure composed of alternating layers of donor–acceptor columns of different orientations upon cocrystallisation with TCNQ.