ABSTRACT
Mineral spring water is a top quality potable groundwater resource formed by long-term groundwater-rock interaction in aquifer. Mineral spring water is rich in minerals and trace elements which are beneficial for human health. Given the current serious water pollution and environment deterioration, it is of great significance to re-recognize the ecological and health effects of mineral water based on new scientific and technological achievement. The Wudalianchi scenic area in Heilongjiang Province has abundant mineral water and peloid resources, which supported the development of tourism and convalescence and have been used in medical and health care for more than 100 years. However, it is threatened by resource reduction, environmental pollution, and other problems. Here, we reviewed the formation process, distribution, hydro-biochemical characteristics and health effects of the Wudalianchi mineral springs, with particular focus on the advances of microbial studies in this area. We also proposed the future research prospective for the Wudalianchi mineral water. To better protect and utilize the Wudalianchi mineral water, it was recommended that a green eco-agriculture practice in reducing chemical fertilizers should be adapted in the surrounding farms of Wudalianchi. Along with the development of tourism and recuperation resources, it is necessary to establish a framework of pollution risk assessment and control, and strictly reduce potential emerging pollutants to eco-geological environment.
Subject(s)
Environmental Monitoring , Groundwater/microbiology , Mineral Waters/microbiology , China , Humans , Prospective Studies , Water Pollutants, Chemical/analysisABSTRACT
Fulminates containing the CNO(-) ion have been widely utilized as high-energy density materials (HEDMs) for more than 120 years. Yet no purely covalently bound CNO molecule, i.e., nitrile oxide, is known to behave as an HEDM. In this study, we performed a thorough investigation of the potential energy surface of nitrile oxide ONCNO and related isomers, applying various sophisticated methods including G4, CBS-QB3, W1BD, CCSD(T)/CBS, and CASPT2/CBS. The Gibbs free energy calculations showed that the decomposition of ONCNO to the considerably endothermic products CNO + NO is favored compared to that into the highly exothermic products CO2 + N2. Thus, ONCNO fails to be the long expected nitrile oxide HEDM. However, with the rate-determining barrier of 23.3 kcal mol(-1) at the W1BD level, ONCNO should be experimentally accessible.
ABSTRACT
The inverse sandwich Ca-C8H8-Ca is predicted to be an open-shell singlet state. Since the C8H8 ligand prevents the spin-up and spin-down electrons of different calcium atoms from forming Ca-Ca bonds, the spin-coupling electrons lead to a singlet diradical character. The metal-ligand interaction contributes to the stability of Ca-C8H8-Ca against dissociation and isomerization. For the coordination complex (DME)3Ca-C8H8-Ca(DME)3, the open-shell singlet state is unavailable, while the closed-shell singlet state with direct Ca-Ca bonds is more favorable, because dimethyl ether molecules could push the spin-paired electrons of different calcium atoms to migrate towards the direction of Ca-Ca bonding. For Ca-C4H4-Ca, the ground state is an open-shell singlet state, of which the diradical character is very similar to that of Ca-C8H8-Ca. For (DME)3Ca-C4H4-Ca(DME)3, the lowest energy is the triplet state.
ABSTRACT
Reactions of CrCl(2)(THF)(2) with N-aryl-9,10-iminophenanthraquinone in CH(2)Cl(2) give the monoimine chromium complexes (Ar)IPQCrCl(2)(THF)(2) (1, Ar = 2,6-Me(2)C(6)H(3); 2, Ar = 2,6-Et(2)C(6)H(3); 3, Ar = 2,6-(i)Pr(2)C(6)H(3)). Molecular structures of 1 and 3 were revealed to be monomeric with the chromium atoms in distorted octahedral geometries. Similar reactions of CrCl(2)(THF)(2) with N,N-bis(arylimino)phenanthrene ligands afford the diimine complexes (Ar1,Ar2)BIPCrCl(µ-Cl)(3)Cr(THF)(Ar1,Ar2)BIP (4, Ar(1) = Ar(2) = 2,6-Me(2)C(6)H(3); 5, Ar(1) = Ar(2) = 2,6-Et(2)C(6)H(3); 6, Ar(1) = Ar(2) = 2,6-(i)Pr(2)C(6)H(3); 7, Ar(1) = 2,6-Me(2)C(6)H(3), Ar(2) = 2,6-(i)Pr(2)C(6)H(3)). The X-ray diffraction analysis shows that 4, 5, and 7 are chlorine-bridged dimers with each chromium atom in a distorted octahedral geometry. Upon activation with MAO, all these complexes exhibit good catalytic activities for isoprene polymerization affording polyisoprene with predominantly a cis-1,4 unit.
ABSTRACT
Among the fascinating planar tetracoordinate carbon (ptC) species, pentaatomic molecules belong to the smallest class, well-known as "pptC". It has been generally accepted that the planarity of pptC structure is realized via the "delocalization" of the p(z) lone pair at the central carbon and the ligand-ligand bonding interaction. Although "localization" is as key driving force in organic chemistry as "delocalization", the "localization" concept has not been applied to the design of pptC molecules, to the best of our knowledge. In this paper, we apply the "localization" strategy to design computationally a series of new pptC. It is shown that the central carbon atom and one "electronegative" ligand atom X (compared to the Al ligand) effectively form a highly localized C-X multiple bond, converting the lone pair at the central carbon to a two-center two-electron π-bond. At the aug-cc-pVTZ-B3LYP, MP2 and CCSD(T) levels, the designed 18-valence-electron pptC species [XCAl(3)](q); [(X,q) = (B,-2), (C,-1), (N,0)] are found to each possess a stable ptC structure bearing a C-X double bond, indicated by the structural, molecular orbital, Wiberg bonding, potential energy surface and Born-Oppenheimer molecular dynamics (BOMD) analysis. Moreover, our OVGF calculations showed that the presently disclosed (yet previously unconsidered) pptC structure of [C(2)Al(3)](-) could well account for the observed photoelectron spectrum (previously only ascribed to a close-energy fan-like structure). Therefore, [C(2)Al(3)](-) could be the first pptC that bears the highly localized C-X double bond that has been experimentally generated. Notably, the pptC structure is the respective global minimum point for [BCAl(3)](2-) and [NCAl(3)], and the counterion(s) would further stabilize [BCAl(3)](2-) and [C(2)Al(3)](-). Thus, these newly designed pptC species with interesting bonding structure should be viable for future experimental characterization. The presently applied "localization" approach complements well the previous "delocalization" one, indicating that the general "localization vs. delocalization" concept in organic chemistry can be effectively transplanted to exotic pptC chemistry.