Emergent functional behaviour of humic substances perceived as complex labile aggregates of small organic molecules and oligomers

2019 ◽  
Vol 16 (7) ◽  
pp. 505 ◽  
Author(s):  
Elena A. Vialykh ◽  
Dennis R. Salahub ◽  
Gopal Achari ◽  
Robert L. Cook ◽  
Cooper H. Langford
Keyword(s):  
Small Molecules ◽  
Humic Substances ◽  
Humic Acids ◽  
Organic Contaminants ◽  
Environmental Pollutants ◽  
Computational Modelling ◽  
Chemical Properties ◽  
Stacking Interactions ◽  
Aggregation Process ◽  
Π Stacking

Environmental contextThe correlation of physicochemical characteristics of humic substances with their function is crucial to our understanding of how environmental pollutants interact with humic substances. We have developed an approach that models emergent functions of fulvic and humic acids depending on sample characteristics. The results will be useful for predicting the sequestration of organic contaminants in soil under various conditions. AbstractThe structural organisation of humic substances (HS) has been a central question of earth sciences for several decades. The latest experimental results have led to the recognition of HS as complex mixtures of small molecules and oligomers. We investigate the correlation between the chemical composition of HS, perceived as labile aggregates, and the emergent functions. Computational modelling was used to help to understand the processes and mechanisms on the molecular scale that occur in different fractions of the HS, fulvic acids (FA) and humic acids (HA), as they interact with metal ions and organic pollutants. The importance of non-covalent interactions in the emergent functions of HS is highlighted. H-bonding, hydrophilic/hydrophobic surface areas and π-stacking interactions play a significant role in aggregation processes as well as in the sorption of environmental pollutants. In a highly hydrophilic system with small molecules (the SRFA-22 model), H-bonding is the main force that drives the aggregation process. However, in a highly aromatic and hydrophobic model with larger molecular fragments (SRHA-6), hydrophobic and π-stacking interactions dominate in the aggregation process. The chemical properties of contaminants significantly affect their mechanisms of sorption by HS. The interaction of a polar pollutant, phenol, with HS occurs through H-bonding, whereas non-polar benzene interacts through hydrophobic and π-stacking interactions. The non-polar pollutant results in a much stronger sorption by HS and causes an additional structural rearrangement of the aggregates, which make it more stable in the environment.

Examination of Aggregation Induced Enhanced Emission in a Propeller Shaped Chiral- Nonconjugated Blue Emitter from Restricted Intramolecular Rotation and J Type π⋯π Stacking Interactions

2021 ◽  
Author(s):  
Gul Yakali
Keyword(s):  
Thin Film ◽  
Small Molecules ◽  
Solid Phase ◽  
Stacking Interactions ◽  
Optoelectronic Materials ◽  
Π Stacking ◽  
Intramolecular Rotation

Fluorescent organic small molecules with the property of aggregation induced enhanced emission in the solid phase (crystall or thin film) have great attention for the design of optoelectronic materials. Generally,...

scholarly journals Coffee pulp compost: Chemical properties and distribution of humic substances

2012 ◽  
Vol 96 (1-2) ◽  
Author(s):  
Joaquín A. Chong ◽  
José A. Dumas
Keyword(s):  
Humic Substances ◽  
Humic Acids ◽  
Chemical Properties ◽  
Nutrient Release ◽  
Fulvic Acids ◽  
Available Nitrogen ◽  
Total N ◽  
Coffee Pulp ◽  
Compost Amendment ◽  
Ca Ions

The distribution and chemical properties of humic substances (humic acids and fulvic acids) from a twelve-month-old static aerated compost pile of coffee pulp were studied. The compost was separated into five physical granule fractions (500, 1000, 2000, 4000 and 8000 um) in order to determine the effect of particle size on humic substances, on nutrient composition, and on distribution. The objective of this study was to understand the chemical properties and distribution of humic substances in mature coffee pulp compost. There were no significant differences across fractions for total N and available P2O5; these fractions averaged 4.9 and 0.66%, respectively. Potassium (K) increased as fraction size increased, from 3.01 to 3.94%. Readily available nitrogen, NO3 and NH4, was 7.19% of the total N. Eighty-nine percent of the total K was exchangeable K ions, and these varied within compost fractions from 2.82 to 3.33%. Approximately 50% of the total Ca and Mg were exchangeable ions; Ca ions varied from 2.13 to 3.01%, and Mg ions varied from 0.22 to 0.26% among fractions. Sequential extraction of organic carbon showed higher extractable carbon by the extraction with 0.1 N NaOH for 24 h, followed by 0.1 N NaOH for 2 h, and water for 2 h. The optical densities E4/E6 ratio ranged between 6.6 and 8.5 for humic acids (HA) extracted with NaOH for 2 h. The diversity in humic substances (HS) and exchangeable ions among compost fractions indicates that nutrient release is regulated by the size of the granules. In conclusion, these data demonstrate that smaller size particles have greater humification rates, and that N and available P are similar across particle sizes, thus providing an excellent soil compost amendment. 

Self-Recognizing π-π Stacking Interactions Designed for the Generation of Ultrastable Mesoporous Hydrogen-Bonded Organic Frameworks

2019 ◽  
Author(s):  
KAIKAI MA ◽  
Peng Li ◽  
John Xin ◽  
Yongwei Chen ◽  
Zhijie Chen ◽  
...  
Keyword(s):  
Pore Size ◽  
Fiber Composite ◽  
Aqueous Media ◽  
Stacking Interactions ◽  
Mustard Gas ◽  
X Ray Diffraction ◽  
X Ray ◽  
Expansion Strategy ◽  
Π Stacking ◽  
Hydrogen Bonded

Creating crystalline porous materials with large pores is typically challenging due to undesired interpen-etration, staggered stacking, or weakened framework stability. Here, we report a pore size expansion strategy by self-recognizing π-π stacking interactions in a series of two-dimensional (2D) hydrogen–bonded organic frameworks (HOFs), HOF-10x (x=0,1,2), self-assembled from pyrene-based tectons with systematic elongation of π-conjugated molecular arms. This strategy successfully avoids interpene-tration or staggered stacking and expands the pore size of HOF materials to access mesoporous HOF-102, which features a surface area of ~ 2,500 m2/g and the largest pore volume (1.3 cm3/g) to date among all reported HOFs. More importantly, HOF-102 shows significantly enhanced thermal and chemical stability as evidenced by powder x-ray diffraction and N2 isotherms after treatments in chal-lenging conditions. Such stability enables the adsorption of dyes and cytochrome c from aqueous media by HOF-102 and affords a processible HOF-102/fiber composite for the efficient photochemical detox-ification of a mustard gas simulant.

scholarly journals Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1067
Author(s):  
Aleksandra Ukalska-Jaruga ◽  
Romualda Bejger ◽  
Guillaume Debaene ◽  
Bożena Smreczak
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Sorption Properties ◽  
Aliphatic Chains

The objective of this paper was to investigate the molecular characterization of soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are the most reactive soil components. A wide spectrum of spectroscopic (UV–VIS and VIS–nearIR), as well as electrochemical (zeta potential, particle size diameter, and polydispersity index), methods were applied to find the relevant differences in the behavior, formation, composition, and sorption properties of HS fractions derived from various soils. Soil material (n = 30) used for the study were sampled from the surface layer (0–30 cm) of agricultural soils. FAs and HAs were isolated by sequential extraction in alkaline and acidic solutions, according to the International Humic Substances Society method, while HNs was determined in the soil residue (after FAs and HAs extraction) by mineral fraction digestion using a 0.1M HCL/0.3M HF mixture and DMSO. Our study showed that significant differences in the molecular structures of FAs, Has, and HNs occurred. Optical analysis confirmed the lower molecular weight of FAs with high amount of lignin-like compounds and the higher weighted aliphatic–aromatic structure of HAs. The HNs were characterized by a very pronounced and strong condensed structure associated with the highest molecular weight. HAs and HNs molecules exhibited an abundance of acidic, phenolic, and amine functional groups at the aromatic ring and aliphatic chains, while FAs mainly showed the presence of methyl, methylene, ethenyl, and carboxyl reactive groups. HS was characterized by high polydispersity related with their structure. FAs were characterized by ellipsoidal shape as being associated to the long aliphatic chains, while HAs and HNs revealed a smaller particle diameter and a more spherical shape caused by the higher intermolecular forcing between the particles. The observed trends directly indicate that individual HS fractions differ in behavior, formation, composition, and sorption properties, which reflects their binding potential to other molecules depending on soil properties resulting from their type. The determined properties of individual HS fractions are presented as averaged characteristics over the examined soils with different physico-chemical properties.

X-ray Crystal Structure of Gallium Tris- (8-hydroxyquinoline):  Intermolecular π−π Stacking Interactions in the Solid State

1999 ◽  
Vol 11 (3) ◽  
pp. 530-532 ◽  
Author(s):  
Yue Wang ◽  
Weixing Zhang ◽  
Yanqin Li ◽  
Ling Ye ◽  
Guangdi Yang
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Stacking Interactions ◽  
X Ray ◽  
Π Stacking

A macrocyclic [60]fullerene–porphyrin dyad involving π–π stacking interactions

1998 ◽  
pp. 1981-1982 ◽  
Author(s):  
Elke Dietel ◽  
Andreas Hirsch ◽  
Emerich Eichhorn ◽  
Anton Rieker ◽  
Steffen Hackbarth ◽  
...  
Keyword(s):  
Stacking Interactions ◽  
Π Stacking

scholarly journals The influence of biochar on the content of carbon and the chemical transformations of fallow and grassland humic acids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marta Cybulak ◽  
Zofia Sokołowska ◽  
Patrycja Boguta
Keyword(s):  
Humic Acids ◽  
Chemical Properties ◽  
Soil Samples ◽  
Low Molecular Weight ◽  
Organic Carbon Content ◽  
Chemical Transformations ◽  
Limited Information ◽  
Grassland Soils ◽  
Low Degree ◽  
Humification Degree

AbstractThere is limited information regarding the effect of biochar (BioC) on the fertility of fallow and grassland soils, as well as on the properties of their humic acids (HAs). The objective of this study was to evaluate with a 3-year field experiment the influence of BioC on the organic matter (OM) in Haplic Luvisol. BioC (obtained via wood waste pyrolysis at 650 °C) was applied to the soil of subplots under fallow and grassland at doses of 0, 1, 2 and 3 kg m−2. The soil samples were collected eight times. The physicochemical properties were determined for the soil and BioC by analysing the density, pH, surface charge, ash, and organic carbon content. Based on the changes in the structure of the HAs and their quantity in the soils, the chemical properties of the HAs were determined. The maximum BioC dose caused an increase in the content of Corg and HAs. BioC did not influence the humification degree coefficients of the HAs originated from fallow, whereas in the grassland, there were significant changes observed in these coefficient values, indicating that BioC may stimulate and accelerate the humification process of soil HAs. Increasing the BioC doses caused an increase in the soil’s HA content, suggesting an increase in soil sorption capacity. The fluorescence data showed BioC addition to the soil caused an increase in the number of structures characterised by low molecular weight and a low degree of humification.

scholarly journals Isomeric 4,2′:6′,4″- and 3,2′:6′,3″-Terpyridines with Isomeric 4′-Trifluoromethylphenyl Substituents: Effects on the Assembly of Coordination Polymers with [Cu(hfacac)2] (Hhfacac = Hexafluoropentane-2,4-dione)

Inorganics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 54
Author(s):  
Giacomo Manfroni ◽  
Simona S. Capomolla ◽  
Alessandro Prescimone ◽  
Edwin C. Constable ◽  
Catherine E. Housecroft
Keyword(s):  
Coordination Polymers ◽  
Metal Binding ◽  
Polymer Chains ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
Preparative Scale ◽  
X Ray ◽  
Single Crystal Structures ◽  
Π Stacking ◽  
Packing Interactions

The isomers 4′-(4-(trifluoromethyl)phenyl)-4,2′:6′,4″-terpyridine (1), 4′-(3-(trifluoromethyl)phenyl)-4,2′:6′,4″-terpyridine (2), 4′-(4-(trifluoromethyl)phenyl)-3,2′:6′,3″-terpyridine (3), and 4′-(3-(trifluoromethyl)phenyl)-3,2′:6′,3″-terpyridine (4) have been prepared and characterized. The single crystal structures of 1 and 2 were determined. The 1D-polymers [Cu2(hfacac)4(1)2]n.2nC6H4Cl2 (Hhfacac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione), [Cu(hfacac)2(2)]n.2nC6H5Me, [Cu2(hfacac)4(3)2]n.nC6H4Cl2, [Cu2(hfacac)4(3)2]n.nC6H5Cl, and [Cu(hfacac)2(4)]n.nC6H5Cl have been formed by reactions of 1, 2, 3 and 4 with [Cu(hfacac)2].H2O under conditions of crystal growth by layering and four of these coordination polymers have been formed on a preparative scale. [Cu2(hfacac)4(1)2]n.2nC6H4Cl2 and [Cu(hfacac)2(2)]n.2nC6H5Me are zig-zag chains and the different substitution position of the CF3 group in 1 and 2 does not affect this motif. Packing of the polymer chains is governed mainly by C–F...F–C contacts, and there are no inter-polymer π-stacking interactions. The conformation of the 3,2′:6′,3″-tpy unit in [Cu2(hfacac)4(3)2]n.nC6H4Cl2 and [Cu(hfacac)2(4)]n.nC6H5Cl differs, leading to different structural motifs in the 1D-polymer backbones. In [Cu(hfacac)2(4)]n.nC6H5Cl, the peripheral 3-CF3C6H4 unit is accommodated in a pocket between two {Cu(hfacac)2} units and engages in four C–Hphenyl...F–Chfacac contacts which lock the phenylpyridine unit in a near planar conformation. In [Cu2(hfacac)4(3)2]n.nC6H4Cl2 and [Cu(hfacac)2(4)]n.nC6H5Cl, π-stacking interactions between 4′-trifluoromethylphenyl-3,2′:6′,3″-tpy domains are key packing interactions, and this contrasts with the packing of polymers incorporating 1 and 2. We use powder X-ray diffraction to demonstrate that the assemblies of the coordination polymers are reproducible, and that a switch from a 4,2′:6′,4″- to 3,2′:6′,3″-tpy metal-binding unit is accompanied by a change from dominant C–F...F–C and C–F...H–C contacts to π-stacking of arene domains between ligands 3 or 4.

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