Development of a new and high yielding synthetic route to 1,8-diformyl-carbazoles 3 (3a 3,6-di-tert-butyl substituted; 3b 3,6-unsubstituted) is reported. Use of a Heck coupling reaction, followed by ...ozonolysis, has greatly facilitated the preparation of these interesting head units in useful quantities. An initial foray into the new generations of Schiff base macrocycles that ready access to these head units (3) opens up, has led to the direct (i.e., metal-free) synthesis of two 2 + 2 macrocycles from 3a or 3b with 1,2-diaminoethane, H2 L tBu (4a) and H2 L H (4b), respectively, obtained as yellow powders in high yields (87–88%). The dizinc complex Zn2 L H (OAc)2 (5b) was isolated as a bright yellow solid in 83% yield, by 1:2:2 reaction of H2 L H with zinc(II) acetate and triethylamine. Aldehydes 3a and 3b, macrocycle H2 L H , and complex Zn2 L H (OAc)2 (5b) have been structurally characterized. The carbazole NH makes bifurcated hydrogen bonds with the pair of flanking 1,8-diformyl-moieties in 3, or 1,8-diimine-moieties in H2 L H , leading to a flat, all-cis conformation. The stepped conformation of the metal-free macrocycle H2 L H is retained in Zn2 L H (OAc)2, despite deprotonation and binding of two zinc(II) centers within the two tridentate pockets. The N3O2 coordination of the zinc ions is completed by one μ1,1- and one μ1,3- bridging acetate anion. Excitation of nanomolar Zn2 L H (OAc)2 in DMF at 335 nm results in clearly visible blue fluorescence (λmax = 460 nm). Further studies on the H2 L H macrocycle revealed turn-on fluorescence, with selectivity (over Ca2+, Mg2+ and a range of 3d dications) and nanomolar sensitivity for zinc(II) ions, highlighting one of the many potential applications for these new carbazole-based Schiff base macrocycles.
The very different multi-step routes to the closely related pair of diformyl-carbazole head units, 1,8-diformyl-3,6-di-tert-butyl-9H-carbazole (1tBu) and 1,8-diformyl-9H-carbazole (1H), are detailed ...and compared. The first examples of Schiff base macrocycles derived from diformyl-carbazole head units are reported. Specifically, the direct cyclisation of 1tBu or 1H with diethylenetriamine gives the two metal-free 1 + 1 Schiff base macrocycles HLH and HLtBu in high yields. Four carbazole-based macrocyclic complexes, CuIIL(OH2)OAc and NiIILOAc, where L = LH or LtBu, were accessed either by metallation of these macrocycles, or by metal templated reaction of the macrocycle components. CuIILtBu(OH2)OAc·0.5(Ether) and NiLHOAc·EtOH, were structurally characterised, confirming the nickel(ii) complexes are square planar (both show diamagnetic NMR spectra) and that the copper(ii) complexes are square pyramidal with a water molecule bound in the axial site. Like porphyrins, both of these N4-donor macrocycles, which differ only in the R group present at the 3 and 6 positions (H or tBu), impose a strong ligand field.
The very different multi-step routes to the closely related pair of diformyl-carbazole head units, 1,8-diformyl-3,6-di-tert-butyl-9H-carbazole (1tBu) and 1,8-diformyl-9H-carbazole (1H), are detailed ...and compared. The first examples of Schiff base macrocycles derived from diformyl-carbazole head units are reported. Specifically, the direct cyclisation of 1tBu or 1H with diethylenetriamine gives the two metal-free 1 + 1 Schiff base macrocycles HLH and HLtBu in high yields. Four carbazole-based macrocyclic complexes, Cu
L(OH
)OAc and Ni
LOAc, where L = LH or LtBu, were accessed either by metallation of these macrocycles, or by metal templated reaction of the macrocycle components. Cu
LtBu(OH
)OAc·0.5(Ether) and NiLHOAc·EtOH, were structurally characterised, confirming the nickel(ii) complexes are square planar (both show diamagnetic NMR spectra) and that the copper(ii) complexes are square pyramidal with a water molecule bound in the axial site. Like porphyrins, both of these N
-donor macrocycles, which differ only in the R group present at the 3 and 6 positions (H or tBu), impose a strong ligand field.
The synthesis and characterisation of two cobalt(II) complexes, Co
II
L
Br-acr
Cl
2
(1a) and Co
II
L
H-acr
Cl
2
(1b), with acridine head-units resulting from an unexpected ligand rearrangement from ...a diphenylamine head-unit, and the intended cobalt(II) complex, Co
II
L
Br-dpa
(Cl)(H
2
O) (2), are reported. Single crystals of the two dark green acridine-based cobalt(II) complexes, 1a and 1b, form in a one-pot reaction of cobalt(II) chloride, the chosen diphenylamine-2,2′-dicarboxaldehyde (Ia 4,4-′dibromo- or Ib unsubstituted), triethylamine and two equivalents of 2,4-dimethylaniline in acetonitrile, in 23% yield. In contrast, the intended diphenylamine-based complex was isolated in two steps: first isolation of the Schiff base ligand, then complexation with cobalt(II) chloride and deprotonation with potassium tert-butoxide, in methanol/dichloromethane, giving 2 as a bright yellow solid in 67% yield. All three complexes feature cobalt(II) centres, with N
2
Cl
2
approximately tetrahedral coordination for 1a and 1b confirmed by single crystal structure determinations. It is proposed that after one imine 'arm' forms, cobalt(II) coordination facilitates the other aldehyde undergoing an intramolecular cyclisation to form the new heterocyclic acridine head-unit. The structures of both of the resulting acridine-based complexes, 1a and 1b, and that of the originally intended Schiff base ligand, HL
Br-dpa
, were confirmed by single-crystal X-ray diffraction. These are the first examples of complexes of an acridine ligand of this type.
•Concise survey of design, synthesis and properties of 385 complexes of di-ortho-substituted-diarylamine-based ligands.•Tables summarising selected features of the 96 structurally characterised ...complexes.•Summary of biocidal (medicinal, agricultural), to magnetic, electronic and optical, to catalytic (especially polymerisations) applications.•Accessible, attractive and useful reference work for those working in this rapidly expanding area.
First row transition metal (M=Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) complexes of di-o-substituted-diarylamine-based ligands reported prior to April 2014 (identified by SciFinder® Scholar search) are reviewed. Only the 408 complexes where the 3d metal ion is coordinated to the central nitrogen donor atom of this fragment are considered. The ligands identified using this search feature o-substituted aryl groups and include those based on diarylamines, triarylamines, carbazoles, acridines, phenoxazines and dibenzoazepines. The vast majority of the ligands employed are noncyclic, but approximately 40 of the complexes feature macrocyclic ligands. The ligand and metal complex syntheses, as well as the structures of the 96 complexes so characterised, are described. The complexes present a wide range of interesting properties which are also summarised here, including biocidal, magnetic, optical and catalytic activity, the last of these being the most commonly explored.
The bark of Pinus radiata is an under-utilized forest residue that is renewable, abundant and has the potential to become a source of sustainable high-value chemicals. However, the use of this bark ...within a biorefinery for advanced applications is hindered by its intractable characteristics: high integrity, complex composition, and high heterogeneity. Most of the bark is burnt to provide energy and heat. The bark contains a high portion of phenolic extractives, constituting a potential source of valuable compounds. It also contains the heteropolymer suberin, a source of unique building blocks for developing innovative materials with potential broad bactericidal properties. Removal of phenolic extractives and suberin from bark simplifies down-streaming pulping processing of bark’s lignocellulosic part. Herein, we describe an effective green strategy to sequentially extract the lipophilic bark constituents and suberin, exploring scCO2 (40, 50 or 60 °C / 200, 350 or 500 bar) and a biocompatible ionic liquid catalyst. The obtained scCO2 extracts had similar diversity of lipophilic compounds and predominantly contained resin acids. Further extraction of the scCO2 extracted bark yielded suberin amounts of 2.25% wt. The bark’s suberin structure shows archetypal chemical features yet has an idiosyncratic high abundance of alkanoic acids, which is not common in most sources. The findings of this opening bark biorefinery study deserve further development and complementary techno-economic analyses to secure new value chains for the bark's major lipophilic compounds consisting of resin acids and bark suberin.
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•High yield extraction of scCO2 soluble lipophilic compounds from pine bark residues.•scCO2 soluble bark constituents are resin acids, alkan-1-ols, alkanoic acids, and terpenes.•Highly esterified cell wall polymer suberin extracted from bark with an ionic liquid.•Dual potential of bark for sequential recovery of its scCO2 soluble compounds and suberin.•Alkanoic acids are highly abundant (>50% wt) in the isolated bark suberin.
The very different multi-step routes to the closely related pair of diformyl-carbazole head units, 1,8-diformyl-3,6-di-
tert
-butyl-9
H
-carbazole (
1
t
Bu
) and 1,8-diformyl-9
H
-carbazole (
1
H
), ...are detailed and compared. The first examples of Schiff base macrocycles derived from diformyl-carbazole head units are reported. Specifically, the direct cyclisation of
1
t
Bu
or
1
H
with diethylenetriamine gives the two metal-free 1 + 1 Schiff base macrocycles H
L
H
and H
L
t
Bu
in high yields. Four carbazole-based macrocyclic complexes, Cu
II
L
(OH
2
)OAc and Ni
II
L
OAc, where
L
=
L
H
or
L
t
Bu
, were accessed either by metallation of these macrocycles, or by metal templated reaction of the macrocycle components. Cu
II
L
t
Bu
(OH
2
)OAc·0.5(Ether) and Ni
L
H
OAc·EtOH, were structurally characterised, confirming the nickel(
ii
) complexes are square planar (both show diamagnetic NMR spectra) and that the copper(
ii
) complexes are square pyramidal with a water molecule bound in the axial site. Like porphyrins, both of these N
4
-donor macrocycles, which differ only in the R group present at the 3 and 6 positions (H or
t
Bu), impose a strong ligand field.
Practical multi-step routes to 1,8-diformylcarbazole head units, and the first examples of Schiff base macrocycles derived from them, are reported. Like porphyrins, both macrocycles are shown to impose a strong ligand field.
Studies of tropical floodplains have shown that algae are the primary source material for higher consumers in freshwater aquatic habitats. Thus, methods that can predict the spatial variation of ...algal productivity provide an important input to better inform management and conservation of floodplains. In this study, a prediction of the spatial variability in algal productivity was made for the Mitchell River floodplain in northern Australia. The spatial variation of aquatic habitat types and turbidity were estimated using satellite remote sensing and then combined with statistical modelling to map the spatial variation in algal primary productivity. Open water and submerged plants habitats, covering 79% of the freshwater flooded floodplain extent, had higher rates of algal production compared to the 21% cover of emergent and floating aquatic plant habitats. Across the floodplain, the predicted average algal productivity was 150.9 ± 95.47 SD mg C m−2 d−1 and the total daily algal production was estimated to be 85.02 ± 0.07 SD ton C. This study provides a spatially explicit representation of habitat types, turbidity, and algal productivity on a tropical floodplain and presents an approach to map ‘hotspots’ of algal production and provide key insights into the functioning of complex floodplain–river ecosystems. As this approach uses satellite remotely sensed data, it can be applied in different floodplains worldwide to identify areas of high ecological value that may be sensitive to development and be used by decision makers and river managers to protect these important ecological assets.
Floodplain wetlands provide an important subsidy for riverine food webs as sites of high algal production. However, this subsidy depends on the degree of landscape connectivity during flood pulses, ...which provides the opportunity for movement of higher order consumers between rivers and floodplains to access these productive habitats. Changes in floodplain inundation extent and duration, due to variable wet season flows or water resource development (WRD), can impact landscape connectivity and ultimately the magnitude of the food web subsidy.
We explored landscape connectivity using graph theory and derived four new metrics to measure how different flow scenarios can affect connectivity and algal production. We considered a historic scenario with the present level of water resource development in our study area, the Mitchell River, and a WRD scenario with the inclusion of three new dams in the catchment. We generated 240 unique daily spatial graphs, using surface water inundation maps across 40‐day flood events to compare a dry year (2006), an average flow year (2001) and a wet year (2009) with and without a WRD scenario.
Drier years and WRD scenario resulted in floodplain fragmentation, potentially constraining the movement of higher order consumers. Changes in connectivity due to WRD resulted in predicted reductions of up to 26% of algal production on the floodplain that was otherwise connected to the main river channels.
Synthesis and applications. The approach developed in this study provides new metrics to identify how changes in floodplain surface water extent due to water resource development and climatic variation may impact ecosystem function such as connectivity that facilitates access of higher order consumers to primary production in floodplain wetlands. With a direct link to river flow alteration, these metrics can inform catchment planning and management to ensure that the conservation of floodplain ecosystem functions is adequately considered in water resource management decisions.
Resumo
As planícies de inundação fornecem um subsídio importante para cadeias alimentares aquáticas em forma de produção primária. No entanto, esse subsídio depende do grau de conectividade da paisagem durante os pulsos de inundação, o que fornece a oportunidade para o movimento de consumidores entre rios e planícies de inundação para acessar esses habitats produtivos. Mudanças na extensão e duração da inundação da planície de inundação, devido a variações climáticas ou desenvolvimento dos recursos hídricos (DRH), podem impactar a conectividade da paisagem e, em última instância, a magnitude do subsídio de produtores primários para as cadeias alimentares.
Exploramos a conectividade da paisagem usando a teoria dos grafos e derivamos quatro novas métricas para medir como os diferentes cenários de inundação podem afetar a conectividade e a produção primária. Consideramos um cenário histórico com o nível atual de desenvolvimento de recursos hídricos em nossa área de estudo, o Rio Mitchell, na Austrália, e um cenário DRH com a inclusão de três novas barragens na bacia hidrográfica. Geramos 240 gráficos diários, usando mapas de inundação em eventos de inundação de 40 dias para comparar um ano seco (2006), um ano de fluxo médio (2001) e um ano úmido (2009), nos cenários histórico e DRH.
Anos mais secos e os cenários DRH resultaram na fragmentação da planície de inundação, potencialmente restringindo o movimento de consumidores. Mudanças na conectividade devido ao DRH resultaram em reduções previstas de até 26% da produção primária na planície de inundação que de outra forma estava conectada aos canais principais do rio Mitchell.
Síntese e aplicações. Esta abordagem fornece novas métricas para identificar como as mudanças na extensão da água superficial da planície de inundação e na conectividade podem impactar o funcionamento do ecossistema, como o potencial acesso de consumidores de ordem superior à produção primária em áreas úmidas da planície de inundação. Com uma ligação direta à alteração da vazão do rio, essas métricas podem informar o planejamento e gestão da bacia para garantir que a conservação das funções do ecossistema da planície de inundação seja adequadamente considerada sob os impactos futuros da gestão dos recursos hídricos.
The approach developed in this study provides new metrics to identify how changes in floodplain surface water extent due to water resource development and climatic variation may impact ecosystem function such as connectivity that facilitates access of higher order consumers to primary production in floodplain wetlands. With a direct link to river flow alteration, these metrics can inform catchment planning and management to ensure that the conservation of floodplain ecosystem functions is adequately considered in water resource management decisions.
Floodplain wetlands are among the most productive and biodiverse ecosystems on Earth and provide a major subsidy of food resources for consumers in river systems. The basal energy source for those ...consumers in many systems comes from aquatic algal production influenced by different characteristics of the floodplain environment. Our aim was to estimate relationships between algal productivity and environmental variables in the channels and wetlands of the Mitchell River floodplain in tropical Australia. We measured physical, chemical, and biological variables in a range of different wetland types (palustrine, lacustrine, and riverine) and different habitat types (emergent macrophytes, floating macrophytes, submerged macrophytes, and open water). The most productive areas were found among riverine wetlands and submerged habitats. The statistical models showed that habitat type and turbidity alone can predict algal productivity with reasonable accuracy (pseudo-R
2
= 0.35, n = 63). Importantly, those attributes can be measured using remote sensing, and hence the model can be used to predict algal productivity over wider spatial scales and identify important "hotspot" areas of primary productivity that sustain aquatic food webs. Through this approach we can inform current conservation and water planning frameworks to manage the impact of human development on the productivity of wetlands at large spatial scales.
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