Assessing the Seasonal and Spatial Dynamics of Zooplankton through DNA Metabarcoding in a Temperate Estuary.

Zooplankton are key components of estuarine trophic networks. However, routine monitoring is hindered by the difficulty of morphology-based identification. DNA-based methods allow us to circumvent some of these hurdles, providing precise species identifications regardless of the taxonomic expertise of the investigator or the developmental stage of the specimens. However, the process is dependent on the completeness of the reference libraries. In this study, we sought to evaluate the potential of DNA metabarcoding to assess the seasonal (summer, autumn, and early spring) and spatial dynamics of zooplankton (four locations spanning ca. 6 km) in the Lima estuary (NW Portugal). Two genetic markers were used: the cytochrome c oxidase subunit I and the V4 hypervariable region of the ribosomal 18S rRNA genes. Overall, 327 species were recovered, and both markers displayed minute overlap (7% were detected with both markers). Species richness, composition, and taxonomic distinctness were majorly influenced by the season, with a declining tendency from summer (highest number of exclusive species, n = 74) to spring. Second to season, the taxa composition was influenced by spatial variation where the most downstream site displayed the highest number of exclusive species, n = 53. A total of 16 non-indigenous species were detected using metabarcoding, but only one (Austrominus modestus) has been documented out in the estuary. In conclusion, both the seasonal and spatial gradients influenced the recovered richness, composition, and taxonomic distinctness, confirming the great aptitude of DNA metabarcoding for providing higher density monitoring and shedding new light on the composition and dynamics of complex zooplankton communities.

New copper(I) complexes of bulky 5-substituted-2-iminopyrrolyl ligands as catalysts for azide-alkyne cycloaddition.

Five dinuclear copper(I) complexes of the type [Cu{κN,κN'-5-R-NC4H2-2-C(H)N(2,6-iPr2C6H3)}]2 (1a-e; R = 2,4,6-iPr3C6H2 (a), R = 2,6-Me2C6H3 (b), R = 3,5-(CF3)2C6H3 (c), R = 2,6-(OMe)2C6H2 (d), R = CPh3 (e)) were prepared by the reaction of the respective 5-R-2-iminopyrrolyl potassium salts KLa-e and [Cu(NCMe)4]BF4 in moderate yields. These new copper(I) complexes were characterized by NMR spectroscopy, elemental analysis and, in selected cases, by single crystal X-ray diffraction and their structural and electronic features further analyzed by DFT calculations and cyclic voltammetry, respectively. X-ray diffraction studies reveal dimeric Cu structures assembled by 2-iminopyrrolyl bridging ligands adopting a transoid conformation (complexes 1a and 1d), while complexes 1c and 1e displayed a cisoid conformation of those moieties, with respect to the Cu(I) centers. Additionally, VT-1H NMR and 1H-1H NOESY NMR experiments on complexes 1a-e exhibited complex fluxional processes in solution, assigned to a conformational inversion of the respective Cu2N4C4 metallacycles in all complexes but 1c, accompanied by a cisoid-transoid isomerization in the cases of complexes 1d,e. The Cu(I) complexes were also analyzed by cyclic voltammetry, where all complexes exhibit two oxidation processes, where the first oxidation is reversible, with the exception of 1b and 1c, which also show the highest oxidation potentials. The oxidation potentials follow clear trends related to the structural parameters of the complexes, in particular the Cu⋯Cu distance and the Cu2N4C4 macrocycles torsion angles. All new 5-substituted-2-iminopyrrolyl Cu(I) complexes 1a-e served as catalysts for azide-alkyne cycloaddition (CuAAC) reactions, being able to generate the respective 1,2,3-triazole products in yields as high as 82% and turnover frequencies (TOFs) as high as 859 h-1, after optimizing the conditions. The activity, as measured by the TOF, is in accordance with the oxidation potential of the corresponding complexes, the easier the oxidation, the higher the TOF value. Complex 1-H, where R = H, proved to be a poor catalyst for the same reactions, indicating that the 5-substitution in the ligand framework is crucial in stabilizing any potential catalytic species.

9-Borafluoren-9-yl and diphenylboron tetracoordinate complexes of F- and Cl-substituted 8-quinolinolato ligands: synthesis, molecular and electronic structures, fluorescence and application in OLED devices.

Six new four-coordinate tetrahedral boron complexes, containing 9-borafluoren-9-yl and diphenylboron cores attached to orthogonal fluorine- and chlorine-substituted 8-quinolinolato ligand chromophores, have been synthesised, characterised, and applied as emitters in organic light-emitting diodes (OLEDs). An extensive steady-state and time-resolved photophysical study, in solution and in the solid state, resulted in the first-time report of delayed fluorescence (DF) in solid films of 8-quinolinolato boron complexes. The DF intensity dependence on excitation dose suggests that this emission originates from triplet-triplet annihilation (TTA). Density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies give insight into the ground and excited state geometries, electronic structures, absorption energies, and singlet-triplet gaps in these new organoboron luminophores. Finally, given their highly luminescent behaviour, organic light-emitting diode (OLED) devices were produced using the synthesised organoboron compounds as emissive fluorescent dopants. The best OLED displays green-blue (λmaxEL = 489 nm) electroluminescence with an external quantum efficiency (EQE) of 3.3% and a maximum luminance of 6300 cd m-2.

Enhancing SIM behaviour in a mononuclear tetrahedral [Co(N,N'-2-iminopyrrolyl)2] complex.

A new homoleptic Co(II) complex bearing two highly sterically congested 2-formiminopyrrolyl N,N'-chelating ligands is reported, displaying slow relaxation of the magnetisation at zero static (DC) field. This compound shows a large value for the zero-field splitting (ZFS) parameter D of -42.6(4) cm-1 leading to a spin-reversal energy barrier Ueff of 85 cm-1.

Hydrosilylation of Aldehydes and Ketones Catalyzed by a 2-Iminopyrrolyl Alkyl-Manganese(II) Complex.

A well-defined and very active single-component manganese(II) catalyst system for the hydrosilylation of aldehydes and ketones is presented. First, the reaction of 5-(2,4,6-iPr3C6H2)-2-[N-(2,6-iPr2C6H3)formimino]pyrrolyl potassium (KL) and [MnCl2(Py)2] afforded the binuclear 2-iminopyrrolyl manganese(II) pyridine chloride complex [Mn2{κ2N,N'-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}2(Py)2(µ-Cl)2] 1. Subsequently, the alkylation reaction of complex 1 with LiCH2SiMe3 afforded the respective (trimethylsilyl)methyl-Mn(II) complex [Mn{κ2N,N'-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}(Py)CH2SiMe3] 2 in a good yield. Complexes 1 and 2 were characterized by elemental analysis, 1H NMR spectroscopy, Evans' method, FTIR spectroscopy, and single-crystal X-ray diffraction. While the crystal structure of complex 1 has been identified as a binuclear entity, in which the Mn(II) centers present pentacoordinate coordination spheres, that of complex 2 corresponds to a monomer with a distorted tetrahedral coordination geometry. Complex 2 proved to be a very active precatalyst for the atom-economic hydrosilylation of several aldehydes and ketones under very mild conditions, with a maximum turnover frequency of 95 min-1, via a silyl-Mn(II) mechanistic route, as asserted by a combination of experimental and theoretical efforts, the respective silanes were cleanly converted to the respective alcoholic products in high yields.

Two better than one: The complementary of different types of artificial substrates on benthic marine macrofauna studies.

Non-destructive methodologies based on the use of artificial substrates (AS) for quantitative sampling of macrofauna have been used to solve sampling problems in complex benthic environment, such as rocky reefs. The macrofauna assemblages of two different types of AS (dendritic and crevice), at two different locations were studied. The main goal was to evaluate the complementarity of dendritic and crevice AS when sampling the macrofauna associated with rocky environments, in two scenarios: within the same location and between locations. With this approach, we intend to contribute to the development of a non-destructive sampling methodology based on AS. The hypotheses tested were that i) the assemblages associated with each type of AS would differ between them and, ii) regardless of AS type, assemblages would differ between locations. Our results revealed significant differences after three months between the macrofauna assemblages from dendritic and crevice substrates in both locations and differences between locations irrespective of the AS type used. Hence, due to the high number of species that only were attracted by each type of AS and the species settlement preferences, our findings have shown the complementarity of the two types of AS (dendritic and crevice). This suggests that the mixed use of AS could be the best approach to non-destructive standard monitoring programs based on benthic marine macrofauna.

Luminescent halogen-substituted 2-(N-arylimino)pyrrolyl boron complexes: the internal heavy-atom effect.

A group of new boron complexes [BPh2{κ2N,N'-NC4H3-2-C(H)[double bond, length as m-dash]N-C6H4X}] (X = 4-Cl 4c, 4-Br 4d, 4-I 4e, 3-Br 4f, 2-Br 4g, 2-I 4h) containing different halogens as substituents in the N-aryl ring have been synthesized and characterized in terms of their molecular properties. Their photophysical characteristics have been thoroughly studied in order to understand whether these complexes exhibit an internal heavy-atom effect. Phosphorescence emission was found for some of the synthesized halogen-substituted boron molecules, particularly for 4g and 4h. DFT and TDDFT calculations showed that the lower energy absorption band resulted from the HOMO to LUMO (π-π*) transition, except for 2-I 4h, where the HOMO-1 to LUMO transition was also involved. The strong participation of iodine orbitals in HOMO-1 is reflected in the calculated absorption spectra of the iodine derivatives, especially 2-I 4h, when spin-orbit coupling (SOC) was included. Organic light-emitting diodes (OLEDs) based on these complexes, in the neat form or dispersed in a matrix, were also fabricated and tested. The devices based on films prepared by thermal vacuum deposition showed the best performance. When neat complexes were used, a maximum luminance (Lmax) of 1812 cd m-2 was obtained, with a maximum external quantum efficiency (EQEmax) of 0.15%. An EQEmax of ca. 1% along with a maximum luminance of 494 cd m-2 were obtained for a device fabricated by co-deposition of the boron complex and a host compound (1,3-bis(N-carbazolyl)benzene, mCP).

Boron complexes of aromatic 5-substituted iminopyrrolyl ligands: synthesis, structure, and luminescence properties.

A group of new mononuclear boron chelate compounds [BPh2{κ2N,N'-5-R-NC4H2-2-C(H)[double bond, length as m-dash]N-Ar}] (R = Ar = C6H57; R = C6H5, Ar = 2,6-iPr2C6H38; R = Anthracen-9-yl (Anthr), Ar = C6H59; R = Anthr, Ar = 2,6-iPr2C6H310) were synthesized via the reaction of B(C6H5)3 with the corresponding 5-substituted 2-(N-arylformimino)pyrrole ligand precursors 3-6. These complexes were prepared in order to evaluate the luminescence potential derived from the substitution of the position 5 of the pyrrolyl ring with an aromatic group. Compounds 7-10 were photophysically characterized in solution and in the solid state. The 5-phenyl-2-iminopyrrolyl-BPh2 complexes 7 and 8 are blue emitters and have enhanced photoluminescence quantum yields in the solid state (ΦPL) up to 0.95, whereas the 5-anthracenyl derivatives 9 and 10 have green-bluish fluorescence and a ΦPL of 0.49 and 0.24, respectively. DFT and TDDFT studies were performed, considering the effect of solvent and dispersion, in order to show how the geometries of compounds 7-10 changed from the ground to the excited state, to assign electronic transitions, and to rationalize the observed luminescence. These materials were applied in organic light-emitting diodes (OLEDs), with various device structures, the best showing an external quantum efficiency of 2.75% together with a high luminance of 23 530 cd m-2.

Cobalt(I) Complexes of 5-Aryl-2-iminopyrrolyl Ligands: Synthesis, Spin Isomerism, and Application in Catalytic Hydroboration.

This work reports the first successful isolation and full characterization of cobalt(I) complexes of 5-aryl-2-iminopyrrolyl ligands. In one approach, when [Co{κ2 N,N'-5-(2,4,6-R3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(Py)Cl] (R = iPr, 1a; R = Ph, 1b) were reacted with K(HBEt3) or Na(Hg) in toluene, the Co(I) arene complexes [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(η6-C6H5CH3)] (2a) and [ Co{κ2 N,N'-5-[2'-(κ:η6- C6H5)-C6H2-4',6'-Ph2]-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}] (2b) were formed. The reaction of complex 1a with KC8 in Et2O yielded the [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}]2 (3). On another approach, the metathesis of potassium 5-(2,4,6-triisopropylphenyl)-2-( N-2,6-diisopropylphenylformimino)pyrrolyl (KLa) with CoCl(PMe3)3 yielded the bis(trimethylphosphine) complex [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(PMe3)2] (4) in a good yield. Complexes 2a, 3, and 4 are paramagnetic, high-spin species, while 2b is a diamagnetic complex. Compound 2b exhibited a spin isomerism behavior ( S = 0 ↔ S = 1) as determined by variable-temperature 1H NMR experiments (Δ H° = 7.7 kcal mol-1), being also supported by computational studies (Δ E = 4.2 kcal mol-1). All complexes were tested in the hydroboration of styrene with pinacolborane (HBPin), with complex 4 exclusively yielding the respective anti-Markovnikov addition product. Additionally, all complexes catalyzed the fast and quantitative hydroboration of benzaldehyde with HBPin.

New phenyl-nickel complexes of bulky 2-iminopyrrolyl chelates: synthesis, characterisation and application as aluminium-free catalysts for the production of hyperbranched polyethylene.

A family of mono(2-iminopyrrolyl) complexes with the general formula [Ni{κ2N,N'-5-(aryl)-NC4H2-2-C(H)[double bond, length as m-dash]N-2,6-(aryl)}(C6H5)(PPh3)] were obtained from the reaction of the sodium salts of the newly synthesised 5-aryl-2-(N-arylformimino)pyrroles with the square planar complex trans-[Ni(C6H5)(PPh3)2Cl]. These new iminopyrrole ligand precursors, designed with increasing bulkiness and different electronic properties, and their corresponding nickel(ii) complexes were characterised by NMR spectroscopy and elemental analysis, and their structural features were analysed by single crystal X-ray diffraction. The nickel complexes were tested as aluminium-free catalysts for the polymerisation of ethylene, at low to moderate pressures and different temperatures and in the absence or presence of the phosphine scavenger [Ni(COD)2], giving rise to catalytic activities in the range of 3.61-73.12 kgPE molNi-1 h-1 bar-1. The polyethylene products formed in these catalytic reactions were characterised by GPC/SEC and NMR spectroscopy. Generally, low molecular weight (Mn 510-1300 g mol-1) low viscosity oils were obtained, presenting high branching degrees (80-125 branches per 1000 C atoms), which are characteristic of hyperbranched polyethylene products. In particular, polymerisation reactions using catalyst 7 led to higher viscosity oils with molecular weights between 11 000 and 20 000 g mol-1, and branching degrees of 100-120 branches per 1000 C atoms.

Hydroboration of Terminal Olefins with Pinacolborane Catalyzed by New Mono(2-Iminopyrrolyl) Cobalt(II) Complexes.

The 5-substituted 2-aryliminopyrrolyl ligand precursors of the type 5-R-2-[ N-(2,6-diisopropylphenyl)formimino]-1 H-pyrrole (R = 2,6-Me2-C6H3 (1a), 2,4,6-iPr3-C6H2 (1b), 2,4,6-Ph3-C6H3 (1c; reported in this work), anthracen-9-yl (1d), CPh3 (1e; reported in this work)) were treated with K[N(SiMe3)2] in toluene to yield the respective 5-R-2-[ N-(2,6-diisopropylphenyl)formimino]pyrrolyl potassium salts 2a-e in high yields. The paramagnetic 15-electron Co(II) complexes of the type [Co{κ2 N,N'-5-R-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(Py)Cl] (3a-e; Py = pyridine) were prepared by salt metathesis of CoCl2(Py)4 with the respective potassium salts 2a-e in moderate to good yields. When the CoCl2(THF)1.5 precursor was combined with the in situ prepared sodium salt of ligand precursor 1b, the trinuclear complex [Co{κ2 N, N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(µ-Cl)]2[(µ-Cl)2Co(THF)2] (4) was obtained in high yields. Complexes 3a-e have high-spin electronic configurations both in solution and in the solid state. X-ray diffraction studies of complexes 3a,e confirmed distorted tetrahedral coordination geometries. Complex 4, on the other hand, is a linear trinuclear Co(II)-Co(II)-Co(II) complex with two terminal distorted tetrahedral four-coordinate sites and a central octahedral six-coordinate site, all in the high-spin state, S = 3/2, as confirmed by the magnetization measurements and DFT calculations. Solid-state magnetic measurements in both complexes 3a and 4 point to paramagnetic behavior with a significant contribution of spin-orbit coupling. Additionally, intramolecular antiferromagnetic coupling of the adjacent cobalt atoms is observed in 4. The Co(II) family 3a-d, on activation with K(HBEt3), catalyzed the hydroboration of several α-olefins with pinacolborane, in good to high yields (50-80%). This system almost exclusively yielded the anti-Markovnikov (a-Mk) addition product, except when styrene was used, where the selectivity in the Markovnikov (Mk) product increased with increasing steric bulkiness of the 5-R-2-iminopyrrolyl substituent, with the a-Mk:Mk molar ratio varying from 2.33:1 (3a, R = 2,6-Me2-C6H3) to 0.75:1 (3c, R = 2,4,6-Ph3-C6H3). Preliminary mechanistic studies indicate that the activation by K(HBEt3) gave rise to a Co(I) species, the catalyst system likely following an oxidative addition pathway.

Synthesis and Characterization of Isosorbide-Based Polyurethanes Exhibiting Low Cytotoxicity Towards HaCaT Human Skin Cells.

The synthesis of four samples of new polyurethanes was evaluated by changing the ratio of the diol monomers used, poly(propylene glycol) (PPG) and D-isosorbide, in the presence of aliphatic isocyanates such as the isophorone diisocyanate (IPDI) and 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI). The thermal properties of the four polymers obtained were determined by DSC, exhibiting Tg values in the range 55⁻70 °C, and their molecular structure characterized by FTIR, ¹H, and 13C NMR spectroscopies. The diffusion coefficients of these polymers in solution were measured by the Pulse Gradient Spin Echo (PGSE) NMR method, enabling the calculation of the corresponding hydrodynamic radii in diluted solution (1.62⁻2.65 nm). The molecular weights were determined by GPC/SEC and compared with the values determined by a quantitative 13C NMR analysis. Finally, the biocompatibility of the polyurethanes was assessed using the HaCaT keratinocyte cell line by the MTT reduction assay method showing values superior to 70% cell viability.

ILs through the looking glass: electrostatics and structure probed using charge-inverted ionic liquid pairs.

Ionic liquids combining potassium cations with 1-alkyl-3-methylcyclopentadienyl anions, K[CnC1Cp] (n = 4, 6) have been synthesized. Differential scanning calorimetry measurements have shown that K[C4C1Cp] and K[C6C1Cp] melt without decomposition at around 90 °C. These two ionic liquids are the charge-inverted counterparts of [C4C1Im]Cl and [C6C1Im]Cl, two common ionic liquids. The concept of charge-inverted ionic pairs is used to explore the nature of the interactions and structure in different ionic compounds, from simple alkali halide salts to ionic liquids based on complex molecular ions. Different sets of experimental data, empirical correlations and molecular dynamics simulations are used to that effect.

Boron complexes of aromatic ring fused iminopyrrolyl ligands: synthesis, structure, and luminescence properties.

The condensation reactions of 2-formylindole (1) or 2-formylphenanthro[9,10-c]pyrrole (2) with various aromatic amines afforded the corresponding phenyl or phenanthrene ring fused mono-/bis-iminopyrrole ligand precursors 3-8, which, upon reaction with BPh3 in an appropriate molar ratio, led to the new mono- and diboron chelate compounds Ph2B[NC8H5C(H)[double bond, length as m-dash]N-2,6-Ar] (Ar = 2,6-iPr2C6H39; C6H510), Ph2B[(NC8H5C(H)[double bond, length as m-dash]N)2-1,4-C6H4]BPh211, Ph2B(NC16H9C(H)[double bond, length as m-dash]N-Ar) (Ar = 2,6-iPr2C6H312; C6H513), and Ph2B[(NC16H9C(H)[double bond, length as m-dash]N)2-1,4-C6H4]BPh214, respectively. Boron complexes 12-14, containing a phenanthrene fragment fused to the pyrrolyl C3-C4 bond, are highly fluorescent in solution, with quantum efficiencies of 37%, 61% and 58% (in THF), respectively, their emission colours ranging from blue to orange depending on the extension of π-conjugation. Complexes 9-11, containing a benzene fragment fused to the pyrrolyl C4-C5 bond, are much weaker emitters, exhibiting quantum efficiencies of 10%, 7% and 6%, respectively. DFT and TDDFT calculations showed that 2,6-iPr2C6H3N-substituents or, to a smaller extent, the indolyl group prevent a planar geometry of the ligand in the excited state and reveal the existence of a low energy weak band in all the indolyl complexes, which is responsible for the different optical properties. Non-doped single-layer light-emitting diodes (OLEDs) were fabricated with complexes 9-14, deposited by spin coating, that of complex 13 revealing a maximum luminance of 198 cd m-2.

Starting a DNA barcode reference library for shallow water polychaetes from the southern European Atlantic coast.

Annelid polychaetes have been seldom the focus of dedicated DNA barcoding studies, despite their ecological relevance and often dominance, particularly in soft-bottom estuarine and coastal marine ecosystems. Here, we report the first assessment of the performance of DNA barcodes in the discrimination of shallow water polychaete species from the southern European Atlantic coast, focusing on specimens collected in estuaries and coastal ecosystems of Portugal. We analysed cytochrome oxidase I DNA barcodes (COI-5P) from 164 specimens, which were assigned to 51 morphospecies. To our data set from Portugal, we added available published sequences selected from the same species, genus or family, to inspect for taxonomic congruence among studies and collection location. The final data set comprised 290 specimens and 79 morphospecies, which generated 99 Barcode Index Numbers (BINs) within Barcode of Life Data Systems (BOLD). Among these, 22 BINs were singletons, 47 other BINs were concordant, confirming the initial identification based on morphological characters, and 30 were discordant, most of which consisted on multiple BINs found for the same morphospecies. Some of the most prominent cases in the latter category include Hediste diversicolor (O.F. Müller, 1776) (7), Eulalia viridis (Linnaeus, 1767) (2) and Owenia fusiformis (delle Chiaje, 1844) (5), all of them reported from Portugal and frequently used in ecological studies as environmental quality indicators. Our results for these species showed discordance between molecular lineages and morphospecies, or added additional relatively divergent lineages. The potential inaccuracies in environmental assessments, where underpinning polychaete species diversity is poorly resolved or clarified, demand additional and extensive investigation of the DNA barcode diversity in this group, in parallel with alpha taxonomy efforts.

First examples of neutral and cationic indenyl nickel(II) complexes bearing arsine or stibine ligands: highly active catalysts for the oligomerisation of styrene.

New indenyl nickel(ii) complexes bearing arsine or stibine ligands synthesised by a new methodology exhibit very high catalytic activities for the oligomerisation of styrene.

Luminescent Di- and Trinuclear Boron Complexes Based on Aromatic Iminopyrrolyl Spacer Ligands: Synthesis, Characterization, and Application in OLEDs.

New bis- and tris(iminopyrrole)-functionalized linear (1,2-(HNC4 H3 -C(H)N)2 -C6 H4 (2), 1,3-(HNC4 H3 -C(H)N)2 -C6 H4 (3), 1,4-(HNC4 H3 -C(H)N)2 -C6 H4 (4), 4,4'-(HNC4 H3 -C(H)N)2 -(C6 H4 -C6 H4 ) (5), 1,5-(HNC4 H3 C-(H)N)2 -C10 H6 (6), 2,6-(HNC4 H3 C-(H)N)2 -C10 H6 (7), 2,6-(HNC4 H3 C-(H)N)2 -C14 H8 (8)) and star-shaped (1,3,5-(HNC4 H3 -C(H)N-1,4-C6 H4 )3 -C6 H3 (9)) π-conjugated molecules were synthesized by the condensation reactions of 2-formylpyrrole (1) with several aromatic di- and triamines. The corresponding linear diboron chelate complexes (Ph2 B[1,3-bis(iminopyrrolyl)-phenyl]BPh2 (10), Ph2 B[1,4-bis(iminopyrrolyl)-phenyl]BPh2 (11), Ph2 B[4,4'-bis(iminopyrrolyl)-biphenyl]BPh2 (12), Ph2 B[1,5-bis(iminopyrrolyl)-naphthyl]BPh2 (13), Ph2 B[2,6-bis(iminopyrrolyl)-naphthyl]BPh2 (14), Ph2 B[2,6-bis(iminopyrrolyl)-anthracenyl]BPh2 (15)) and the star-shaped triboron complex ([4',4'',4'''-tris(iminopyrrolyl)-1,3,5-triphenylbenzene](BPh2 )3 (16)) were obtained in moderate to good yields, by the treatment of 3-9 with B(C6 H5 )3 . The ligand precursors are non-emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π-conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time-dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13, in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples (11, 12, 14, and 15), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π-system, to afford green to yellow emissions. Organic light-emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m(-2) , for single layer devices, increasing to 4400 cd m(-2) when a hole-transporting layer is used.

Copper(II) complexes of bis(aryl-imino)acenaphthene ligands: synthesis, structure, DFT studies and evaluation in reverse ATRP of styrene.

Two new Ar-BIAN Cu(II) complexes (where Ar-BIAN = bis(aryl-imino)acenaphthene) of formulations [CuCl2(Mes-BIAN)] (1) (Mes = 2,4,6-Me3C6H2) and [CuCl2(Dipp-BIAN)] (2) (Dipp = 2,6-iPr2C6H3) were synthesised by direct reaction of CuCl2 suspended in dichloromethane with the respective ligands Mes-BIAN (L1) and Dipp-BIAN (L2), dissolved in dichloromethane, under an argon atmosphere. Attempts to obtain these compounds by solubilising CuCl2 in methanol and adding a dichloromethane solution of the corresponding ligand, under aerobic conditions, gave also compound 1, but, in the case of L2, the Cu(I) dimer [CuCl(Dipp-BIAN)]2 (3) was obtained instead of compound 2. The compounds were fully characterised by elemental analyses, MALDI-TOF mass spectrometry, FT-IR, (1)H NMR and EPR spectroscopic techniques. The solid-state molecular structures of compounds 1-3 were determined by single crystal X-ray diffraction, showing the expected chelation of the Ar-BIAN ligands and two chloride ligands completing the coordination sphere of the Cu(II) centre. In the case of the complex 1, an intermediate coordination geometry around the Cu(II) centre, between square planar and tetrahedral, was revealed, while the complex 2 showed an almost square planar geometry. The structural differences and evaluation of energetic changes were rationalised by DFT calculations. Analysis of the electrochemical behaviour of complexes 1-3 was performed by cyclic voltammetry and the experimental redox potentials for Cu(II)/Cu(I) pairs have been compared with theoretical values calculated by DFT in the gas phase and in dichloromethane and methanol solutions. The complex 1 exhibited good activity in the reverse atom transfer radical polymerisation (ATRP) of styrene.

Tunable fluorophores based on 2-(N-arylimino)pyrrolyl chelates of diphenylboron: synthesis, structure, photophysical characterization, and application in OLEDs.

Reactions of 2-(N-arylimino)pyrroles (HNC4H3C(H)=N-Ar) with triphenylboron (BPh3) in boiling toluene afford the respective highly emissive N,N'-boron chelate complexes, [BPh2 {κ(2)N,N'-NC4H3C(H)=N-Ar}] (Ar=C6H5 (12), 2,6-Me2-C6H3 (13), 2,6-iPr2-C6H3 (14), 4-OMe-C6H4 (15), 3,4-Me2-C6 H3 (16), 4-F-C6H4 (17), 4-NO2-C6H4 (18), 4-CN-C6H4 (19), 3,4,5-F3-C6H2 (20), and C6F5 (21)) in moderate to high yields. The photophysical properties of these new boron complexes largely depend on the substituents present on the aryl rings of their N-arylimino moieties. The complexes bearing electron-withdrawing aniline substituents 17-20 show more intense (e.g., ϕf =0.71 for Ar=4-CN-C6H4 (19) in THF), higher-energy (blue) fluorescent emission compared to those bearing electron-donating substituents, for which the emission is redshifted at the expense of lower quantum yields (ϕf=0.13 and 0.14 for Ar=4-OMe-C6H4 (15) and 3,4-Me2-C6H3 (16), respectively, in THF). The presence of substituents bulkier than a hydrogen atom at the 2,6-positions of the aryl groups strongly restricts rotation of this moiety towards coplanarity with the iminopyrrolyl ligand framework, inducing a shift in the emission to the violet region (λmax =410-465 nm) and a significant decrease in quantum yield (ϕf=0.005, 0.023, and 0.20 for Ar=2,6-Me2-C6H3 (13), 2,6-iPr2-C6H3 (14), and C6F5 (21), respectively, in THF), even when electron-withdrawing groups are also present. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have indicated that the excited singlet state has a planar aryliminopyrrolyl ligand, except when prevented by steric hindrance (ortho substituents). Calculated absorption maxima reproduce the experimental values, but the error is higher for the emission wavelengths. Organic light-emitting diodes (OLEDs) have been fabricated with the new boron complexes, with luminances of the order of 3000 cd m(-2) being achieved for a green-emitting device.

Photophysical properties of iminopyrrolyl boron complexes: a DFT interpretation.

The three compounds [BPh(2)(κ(2)N,N'-NC(4)H(3)C(H)=N-C(6)H(5))] (A), [BPh(2)(κ(2)N,N'-NC(4)H(3)C(H)=N-1,4-C(6)H(4)-N=H)C-H(3)C(4)N-N,N'κ(2))BPh(2)] (B) and [BPh(2)(κ(2)N,N'-NC(4)H(3)C(H)=N-4,4'-C(6)H(4)-C(6)H(4)-N=(H)C-H(3)C(4)N-N,N'κ(2))BPh(2)] (C) are blue to green light emitters with average to excellent quantum yields. DFT and TD-DFT calculations were performed in order to understand their behaviour. The geometry of their ground and singlet excited state was optimised, and their absorption patterns and emission were calculated. The large dihedral angles between the planes of the N-aryl and 2-formiminopyrrolyl moieties of the chelating ligand drop considerably, leading to an almost planar geometry in the singlet state. In the three species, the lowest energy absorption occurs at 383, 428, and 419 nm, being calculated at 377, 502, and 529 nm in the gas-phase (slightly shifted in the right direction in THF). It results from a HOMO to LUMO excitation, and was assigned to a transition between π and π* orbitals (ILCT) of the iminopyrrolyl ligand, despite small differences in the exact composition of the HOMO and LUMO in A, B, and C. Introduction of the LB94 functional did not improve the calculated absorption wavelengths, but PBE0 with an all electron basis set within the SOPERT approximation led to better agreement with the experimental absorption maxima and a good reproduction of the excited state lifetimes. The estimated emission wavelengths reproduce the experimental trends.