L Complexes Research Articles

Aza- and Mixed Thia/Aza-Macrocyclic Receptors with Quinoline-Bearing Pendant Arms for Optical Discrimination of Zinc(II) or Cadmium(II) Ions.

The synthesis and coordination properties of two fluorescent chemosensors, featuring [9]aneN3 (1,4,7-triazacyclononane; L1) and [12]aneNS3 (1-aza-4,7,10-trithiacyclododecane; L2) as receptor units, and a quinoline pendant arm with an amide group as a functional group spacer are described. The optical responses of L1 and L2 in the presence of several metal ions were analysed in MeCN/H2 O (1 : 4 v/v) solutions. A selective chelation enhancement of fluorescence (CHEF) effect was observed in the presence of Zn2+ in the case of L1, and in the presence of Cd2+ in the case of L2, following the formation of a 1 : 1 and a 1 : 2 metal/ligand complex, respectively, which was also confirmed by potentiometric measurements. 1 H and 13 C NMR measurements in CD3 CN/CDCl3 in combination with molecular mechanics calculations show that for both complexes of L1 and L2 with Zn2+ and Cd2+ , respectively, the coordination of the carbonyl group from the pendant arm could be the origin of the observed optical selectivity.

Synthesis, Characterization, and DNA-Binding Kinetics of New Pd(II) and Pt(II) Thiosemicarbazone Complexes: Spectral, Structural, and Anticancer Evaluation

In a bid to come up with potential anticancer agents, a class of thiosemicarbazone ligands bearing substituted thiophene were synthesized followed by complexation with various Pd(II) and Pt(II) metal precursors. The ligands (E)-1-((thiophen-2-yl)methylene)thiosemicarbazide (L1), (E)-1-((4-bromothiophen-2-yl)methylene)thiosemicarbazide (L2), and (E)-1-((5-bromothiophen-2-yl)methylene)thiosemicarbazide (L3) were synthesized by condensation reactions and obtained in good yields. Complexation of L1 and L2 with Pd(cod)Cl2 gave C1 (C6H7Cl2N3PdS2) and C2 (C6H6BrCl2N3PdS2), respectively. Complexation of L1 with K2PtCl4 gave C3 (C6H7Cl2N3PtS2), while L3 with K2PtCl2[(PPh)3]2 gave C4 (C24H21BrClN3PPtS2). The structures and coordination for all compounds were established by FTIR, 1H-NMR, 13C-NMR, UV-Vis, elemental analysis, and single-crystal X-ray diffraction studies for ligand L1. Tuning of the spectral and anticancer activity of the compounds was investigated by changing the position of the bromide substituent, metal center, and the σ or π-donor/acceptor strength of the groups surrounding the metal center. The compounds had low to moderate anticancer potency with their spectral and structural properties correlating with the corresponding anticancer activity profiles. DNA binding modes were studied by spectroscopy and were comparable to known DNA intercalators. Structure-activity profiles were evident especially between C1 and C2 differing by the presence of a Br in position 5 of thiophene ring, which caused a remarkable increase in IC50 values, from 14.71 ± 0.016 (C1) to 43.08 ± 0.001(C2) in Caco-2 cells, 1.973 ± 0.048 (C1) to 59.56 ± 0.010 (C2) in MCF-7 cells, 16.65 ± 0.051 (C1) to 72.25 ± 0.003 (C2) in HeLa cells, 14.64 ± 0.037 (C1) to 94.34 ± 0.003 (C2) in HepG2, and 14.05 ± 0.042 (C1) to >100(C2) in PC-3 cells.

Fe(III) bipyridyl or phenanthroline complexes with oxidase-like activity for sensitive colorimetric detection of glutathione.

In this study, three types of Fe(III) bipyridyl or phenanthroline (Fe(III)-L3 ) complex could directly catalyze 3,3',5,5'-tetramethylbenzidine (TMB) to induce blue chromogenic changes without H2 O2 . Fe(III)-L3 complex could induce a colour change in TMB directly after a short incubation time. Due to the high oxidase-like activity of the Fe(III)-L3 complexes, superoxide anion radicals (O2 •- ) were formed in solution. Intermediates radical involving oxo-iron species were then produced that oxidized TMB to its oxidation products (oxTMB), which had an absorbance maximum at 652 nm. Glutathione (GSH) could inhibit the oxidation reaction of the Fe(III)-L3 complex-TMB system, a rapidly colorimetric method was established for the specific detection of GSH that had a detection limit of 0.1 μM. Furthermore, Fe(III)-L3 complexes could catalyze TMB to oxTMB directly without H2 O2 . This fast and simple colorimetric method may open a new avenue for application in the point-of-care diagnosis field using the TMB chromogenic system.

Evaluating Syntactical Complexity in Language Classes An Analysis of the Observations of Italian SL Teachers

This paper aims to investigate how language teachers perceive syntactic complexity in L2 writing and to what extent teachers’ judgments are related to current theoretical views in the research literature on Second Language Acquisition (SLA). Sixteen L2 teachers were asked to evaluate the syntactic complexity of a sample of argumentative texts written by L2 university students of Italian. In the panel discussion that followed, teachers discussed the motivations behind their assigned scores and the feedback they had proposed. The results revealed that teachers tended to focus primarily on accuracy and comprehensibility, and much less on syntactic complexity. Teachers’ reflections appeared to be only partly aligned with existing theoretical views on syntactic complexity in the SLA literature.

Synthesis and Characterization of Copper(I) Halide Complexes Prepared with Bipodal Diacylthioureas

Bipodal diacylthioureas [MesC(O)NHC(S)NH]2R (R = C6H4‐1,2 (L1, 1), C6H4‐1,4 (L2, 2)) were synthesized, and their complexation reactions with equimolar Cu(I) halides CuX (X = Cl, Br, ) were investigated. The obtained ligands L1–2 and the resultant Cu(I) complexes (3–8) were characterized by FT‐IR, 1H NMR, 13C NMR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. The complexation of L1 with CuX gave three different 1D polymers: the infinite single chain (L1CuCl)n (3), edge‐shared double‐ring chain {[(µ‐L1)CuBr]2}n (4), and vertex‐shared double‐ring chain {[L1Cu(µ‐I)]2}n (5). Similarly, but more pronounced, the treatment of L2 with CuX resulted in the formation of 1D edge‐shared double‐ring chain {[(µ‐L2)CuCl]2}n (6), 0D discrete dinuclear metallamacrocyclic ring (L2CuBr)2 (7), and 3D network polymer [L2Cu(µ‐I)]n (8), respectively. The structural diversity may be related to the suitable spacer, flexible C=S directionality and binding roles of halide anions and sulfur donors. Among Cu(I) complexes (3–8) as prepared, both chloride (in 3 and 6) and bromide anions (in 4 and 7) acted as terminal ligands, while the iodide anions (in 5 and 8) served as bridging ligand. In contrast, only in edge‐shared double‐ring chains (4 and 6) it was found that the sulfur donors (one of two in each Ln) played as the bridging ligand.

Synthesis and Elucidation for New Nanosized Cr(III)-Pyrazolin Complexes; Crystal Surface Properties, Antitumor Simulation Studies Beside Practical Apoptotic Path

Synthesis for new pyrazolin derivatives, which oriented for coordination with Cr(III) ion then all new synthesizes were characterized with reliable techniques. Octahedral geometry was the only form suggested from bi-negative tetra-dentate mode of bonding within bi-nuclear complexes. Such offering is based on analytical and spectral tools (IR, UV–Vis and MS). TGA confirms and discriminates water molecules profiles with relative to coordination sphere. Practical and computational XRD patterns appeared having high extent of similarity attributing to nano-crystalline particulate sizes. Hirshfeld surface properties and the efficiency of molecular-contact in crystal-packing, were obtained upon Crystal explorer 3.1 software beside VESTA package. Some physical indices were estimated based on frontier energy gaps over optimized structures upon Gauss-view software. Computational simulation approach was implemented to monitor changes on cancer cell proteins after treatment by new Cr(III) complexes, for assessment. Promising antitumor activity might be expected for Cr(III)-L4, Cr(III)-L3 and Cr(III)-L2 complexes, based on exported interaction parameters. It is worthy to note that, in-vitro assay reflects an excellent cytotoxicity recorded for such three complexes, in excellent harmony with simulation suggestions.

The Relationship Between First and Second Language Writing: Investigating the Effects of First Language Complexity on Second Language Complexity in Advanced Stages of Learning

AbstractRecent studies have uncovered substantial individual differences in first language (L1) language attainment across the lifespan and across multiple components of language. The existence of such variability raises the question of its role in second language (L2) learning. The existing body of research on L1–L2 relationships has primarily targeted reading comprehension by means of controlled experimental designs. This study extended existing research by investigating L1–L2 relationships in writing through the automatic analysis of linguistic complexity in paired samples of authentic production data. For each writing sample, a series of measurements of 12 indicators was obtained using a computational tool that implements a sliding‐window approach. Results from mixed‐effects modeling revealed significant relationships between L1 complexity and L2 complexity for all but one measure, indicating that an L1 effect is robust across different levels of linguistic description.

4+2] Cycloaddition reactions of 1-alkyl-2,3,4,5-tetraphenylphosphole derivatives

The [4+2] cycloaddition reactions of 1-alkyl-2,3,4,5-tetraphenylphosphole derivatives with N-phenylmaleimide were studied for the first time. The reactions of 1-alkyl-2,3,4,5-tetra-phenylphosphole oxides and sulfides with N-phenylmaleimide leads to tricyclic 10-phospha-norbornenes with high stereoselectivity, giving only one diastereomer in the racemic form. At the same time, 1-alkyl-2,3,4,5-tetraphenylphospholes and their W(CO)5L complexes do not undergo [4+2] cycloaddition reactions even upon prolonged heating.

Playing with Structural Parameters: Synthesis and Characterization of Two New Maltol-Based Ligands with Binding and Antineoplastic Properties

Two maltol-based ligands, N,N′-bis((3-hydroxy-4-pyron-2-yl)methyl)-1,4-piperazine (L1) and N,N′,N′-tris((3-hydroxy-4-pyron-2-yl)methyl)-N-methylethylendiamine (L2), were synthesized and characterized. L1 and L2, containing, respectively, two and three maltol units spaced by a diamine fragment, were designed to evaluate how biological and binding features are affected by structural modifications of the parent compound malten. The acid-base behavior and the binding properties towards transition, alkaline-earth (AE) and rare-earth (RE) cations in aqueous solution, studied by potentiometric, UV-Vis and NMR analysis, are reported along with biological studies on DNA and leukemia cells. Both ligands form stable complexes with Cu(II), Zn(II) and Co(II) that were studied as metallo-receptors for AE and RE at neutral pH. L1 complexes are more affected than L2 ones by hard cations, the L1-Cu(II) system being deeply affected by RE. The structural modifications altered the mechanism of action: L1 partially maintains the ability to induce structural alterations of DNA, while L2 provokes single strand (nicks) and to a lesser extent double strand breaks of DNA.

Spin-crossover in iron(II)-phenylene ethynylene-2,6-di(pyrazol-1-yl) pyridine hybrids: toward switchable molecular wire-like architectures

Luminescent oligo(p-phenylene ethynylene) (OPE) and spin-crossover (SCO) active Fe(II)-2,6-di(pyrazol-1-yl) pyridine (BPP) systems are prominent examples proposed to develop functional materials such as molecular wires/memories. A marriage between OPE and Fe(II)-BPP systems is a strategy to obtain supramolecular luminescent ligands capable of metal coordination useful to produce novel spin-switchable hybrids with synergistic coupling between spin-state of Fe(II) and a physical property associated with the OPE skeleton, for example, electronic conductivity or luminescence. To begin in this direction, two novel ditopic ligands, namely L1 and L2, featuring OPE-type backbone end-capped with metal coordinating BPP were designed and synthetized. The ligand L2 tailored with 2-ethylhexyloxy chains at the 2 and 5 positions of the OPE skeleton shows modulated optical properties and improved solubility in common organic solvents relative to the parent ligand L1. Solution phase complexation of L1 and L2 with Fe(BF4)2·6H2O resulted in the formation of insoluble materials of the composition [Fe(L1)]n(BF4)2n and [Fe(L2)]n(BF4)2n as inferred from elemental analyses. Complex [Fe(L1)]n(BF4)2n underwent thermal SCO centred at T1/2 = 275 K as well as photoinduced low-spin to high-spin transition with the existence of the metastable high-spin state up to 52 K. On the other hand, complex [Fe(L2)]n(BF4)2n, tethered with 2-ethylhexyloxy groups, showed gradual and half-complete SCO with 50% of the Fe(II)-centres permanently blocked in the high-spin state due to intermolecular steric interactions. The small angle x-ray scattering (SAXS) pattern of the as-prepared solid complex [Fe(L1)]n(BF4)2n revealed the presence of nm-sized crystallites implying a possible methodology towards the template-free synthesis of functional-SCO nanostructures.

A new route for the synthesis of 2,4-bis(2-pyridyl)-6-(pyridyl)pyrimidines: Synthesis and characterization of Co(II), Ni(II) complexes of 2,4,6-tris(2-pyridyl)pyrimidine

Using 2-acetylpyridine, sodium hydroxide and 2-cyanopyridine, 2,4,6-tris(2-pyridyl)pyrimidine (L1) was synthesized in good yield. Similarly, 2,4-bis(2-pyridyl)-6-(3-pyridyl)pyrimidine (L2) and 2,4-bis(2-pyridyl)-6-(4-pyridyl)pyrimidine (L3) were also synthesized by using respective acetylpyridine. 2-Acetylpyridine reacted with sodium hydroxide to produce 2-oxo-2-(2-pyridyl)-1-ethanide, which behaves as a nucleophile towards 2-cyanopyridine. All three pyrimidines are potential multidentate ligand and by using L1 complexes of composition [Ni(L1)(H2O)3](NO3)2·4H2O (1), [Ni(L1)2](NO3)2·2H2O (2) and [Co(L1)2](NO3)2·1.5H2O (3) were isolated and structurally characterized. In 1–3, L1 behaves as a tridentate pincer type ligand, DFT calculations performed on L1–L3 indicate that energy difference between HOMO and LUMO is 4.544, 4.643 and 4.533 eV respectively.

Theoretical study on noncovalent interaction of molecular tweezers by Zn(II) salphen-azo-crown ether triads receptor.

A novel zinc(II)-salphen-azo-benzo-15-crown-5 triad receptor was studied theoretically as ditopic recognition of hydrophobic amino acid. And density functional theory was used to investigate the Zn(II) salphen-crown ether complex (L1), complex L2 (L1 with the alkaline metal cation Na+), and the corresponding 1:1 sandwich complex (complex L with tryptophan). In this work, geometrical optimization was carried out using ωB97XD functional and def2-SVP basis set for all atoms. The absorption spectra and excited-states were calculated using time-dependent density functional theory and ωB97XD/def2-TZVP level. The absorption spectra data show some significantly shifts in the absorption band due to the present of Na+ or tryptophan. In addition, interfragment interactions between receptor L and tryptophan were analyzed in detail by Independent Gradient Model and topological properties of Bader's atoms in molecules theory, which is found to contribute to forming the metal-ligand bonds, intermolecular H-bond, and van der Waals interaction in 1:1 sandwich complex. The above results demonstrate that the L2 complex is a ditopic receptor to be utilized to recognize amphiphilic molecule - tryptophan.

Synthesis, structure and thermal behavior of volatile mononuclear mixed ligand complexes of rare-earth dipivaloylmethanates with diethylenetriamine

Highly volatile and stable complexes of rare-earth elements with mononuclear structure are of great importance for gas phase deposition of functional thin film materials. Mixed ligand complexes with β-diketonate anions (e.g. thd− = 2,2,6,6-tetrametylheptane-3,5-dionate) and ancillary neutral donor ligands demonstrate mononuclear structure and sufficient volatility, however, they are unstable to neutral ligand elimination especially in case of light rare earth elements. Here diethylenetriamine (deta) has been applied as tridentate neutral ligand to improve the stability of mixed ligand complexes due to macrochelate effect and additional weak intramolecular interactions, e.g. hydrogen bonds. Synthesis of a series of mixed-ligand [Ln(thd)3(deta)], Ln = La (1L), Pr (2L), Nd (3L), Sm (4L) and Gd (5L) complexes, their X-ray single crystal structure characterization, DFT calculations, and thermal behavior study have been performed. Compounds 1L-5L demonstrate similar mononuclear molecular structure, but different molecular packing of three types, which may undergo mutual transformation. Compounds 1L-4L sublime intact in temperature range of 140–160 °C in vacuum without decomposition. 1L was successfully applied as volatile precursors for MOCVD preparation of epitaxial complex oxide thin films, (0 0 l) LaMnO3 and (0 0 l) LaAlO3, on (0 0 l) MgO and (0 0 l) SrTiO3 substrates.

Structural-Dependent N,O-Donor Imine-Appended Cu(II)/Zn(II) Complexes: Synthesis, Spectral, and in Vitro Pharmacological Assessment.

Four mononuclear bioefficient imine-based coordination complexes, [(L1)2Cu], [(L1)2Zn], [(L2)Cu(H2O)], and [(L2)Zn(H2O)], were synthesized using ligands [L1 = 2-(((3-hydroxynaphthalen-2-yl)methylene)amino)-2-methylpropane-1,3-diol and L2 = 4-(1-((1,3-dihydroxy-2-methylpropan-2-yl)imino)ethyl)benzene-1,3-diol]. The formation of the complexes was ascertained by elemental analysis, Fourier transform infrared, 1H NMR, 13C NMR, electrospray ionization–mass spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The comparative binding propensity profiles of the above-synthesized complexes with the DNA/human serum albumin (HSA) were investigated via UV absorption, fluorescence, and Förster resonance energy-transfer studies. On the basis of extended conjugation and planarity, L1 complexes exhibited superior bioactivity with greater calculated DNA binding constant values, (Kb) 2.9444 × 103[(L1)2Cu] and 2.2693 × 103[(L1)2Zn], as compared to L2 complexes, 1.793 × 103[(L2)Cu(H2O)] and 9.801 × 102[(L2)Zn(H2O)]. The competitive displacement assay of complexes was performed by means of fluorogenic dyes (EtBr and Hoechst), which corroborates the occurrence of minor groove binding because of the enhanced displacement activity with Hoechst 33258. The minor groove binding of the [(L1)2Cu] complex is further confirmed by the molecular docking study. Moreover, the HSA study demonstrated effective static quenching of complexes with substantial Ksv values. The [(L1)2Cu] complex was found to have pronounced cleavage efficiency as evaluated from sodium dodecyl sulfate polyacrylamide gel electrophoresis electrophoresis. Furthermore, in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl and superoxide radicals further proclaimed the remarkable bioefficiency of compounds, which make them promising as active chemotherapeutic agents.

Examining Cloze Tests as a Measure of Linguistic Complexity in L2 Writing

Examining Cloze Tests as a Measure of Linguistic Complexity in L2 Writing

Structural and biochemical analysis of the metallo-β-lactamase L1 from emerging pathogen Stenotrophomonas maltophilia revealed the subtle but distinct di-metal scaffold for catalytic activity.

Emergence of Enterobacteriaceae harboring metallo‐β‐lactamases (MBL) has raised global threats due to their broad antibiotic resistance profiles and the lack of effective inhibitors against them. We have been studied one of the emerging environmental MBL, the L1 from Stenotrophomonas maltophilia K279a. We determined several crystal structures of L1 complexes with three different classes of β‐lactam antibiotics (penicillin G, moxalactam, meropenem, and imipenem), with the inhibitor captopril and different metal ions (Zn+2, Cd+2, and Cu+2). All hydrolyzed antibiotics and the inhibitor were found binding to two Zn+2 ions mainly through the opened lactam ring and some hydrophobic interactions with the binding pocket atoms. Without a metal ion, the active site is very similarly maintained as that of the native form with two Zn+2 ions, however, the protein does not bind the substrate moxalactam. When two Zn+2 ions were replaced with other metal ions, the same di‐metal scaffold was maintained and the added moxalactam was found hydrolyzed in the active site. Differential scanning fluorimetry and isothermal titration calorimetry were used to study thermodynamic properties of L1 MBL compared with New Deli Metallo‐β‐lactamase‐1 (NDM‐1). Both enzymes are significantly stabilized by Zn+2 and other divalent metals but showed different dependency. These studies also suggest that moxalactam and its hydrolyzed form may bind and dissociate with different kinetic modes with or without Zn+2 for each of L1 and NDM‐1. Our analysis implicates metal ions, in forming a distinct di‐metal scaffold, which is central to the enzyme stability, promiscuous substrate binding and versatile catalytic activity.StatementThe L1 metallo‐β‐lactamase from an environmental multidrug‐resistant opportunistic pathogen Stenotrophomonas maltophilia K279a has been studied by determining 3D structures of L1 enzyme in the complexes with several β‐lactam antibiotics and different divalent metals and characterizing its biochemical and ligand binding properties. We found that the two‐metal center in the active site is critical in the enzymatic process including antibiotics recognition and binding, which explains the enzyme's activity toward diverse antibiotic substrates. This study provides the critical information for understanding the ligand recognition and for advanced drug development.

Grammatical complexity: ‘What Does It Mean’ and ‘So What’ for L2 writing classrooms?

Grammatical complexity is regarded as a crucial feature of L2 writing. The construct has been widely utilized in empirical research to gauge L2 writing quality and development, particularly in English. Nevertheless, a question of paramount importance, i.e., what constitutes complexity, has not yet received adequate attention. Drawing on Bulté and Housen’s (2012) taxonomy of L2 complexity, we conducted a comprehensive and in-depth review of changes in the definition of grammatical complexity over the past two decades. Our finding suggests that grammatical complexity has been theorized from two primary perspectives: an independent perspective that grammatical complexity is static across different contexts and a dependent perspective that grammatical complexity should be investigated in response to specific registers. Also, grammatical complexity has been observed from primarily the clausal level to the clausal, phrasal and morphological levels, echoing Norris and Ortega’s (2009) claim that grammatical complexity should be studied as a multi-dimensional construct. Moreover, we have identified four main parameters used by existing literatures to define grammatical complexity: length, ratio, index and frequency. The change of each parameter is summarized with details in our review. At the end, we also discuss pedagogical implications for L2 writing instruction in the EAP context.

Investigating teachers’ perceptions of syntactic complexity in L2 academic writing

This paper aims to investigate how L2 teachers perceive syntactic complexity in L2 writing, and to what extent teachers’ judgements are related to current theoretical views. The main reason for conducting the study is that the majority of studies that have investigated the development of syntactic complexity in L2 have been grounded in hypothesis-testing research; few studies, however, have explored whether teachers’ perspectives on syntactic complexity reflect the development of syntactic complexity as hypothesised in the SLA literature. Two groups of language teachers (eleven of L2-Dutch and sixteen of L2-Italian) were asked to evaluate individually the syntactic complexity of a sample of argumentative texts written by L2 university students of, respectively, Dutch and Italian. In the panel discussion that followed, teachers discussed their motivation behind their assigned scores and the feedback they had proposed. The results revealed that teachers tended to focus primarily on accuracy and comprehensibility. When their comments were concerned with syntactic complexity, both similarities and differences (related to target language and writing context) emerged between Dutch and Italian. Teachers’ reflections appeared to be only partly aligned with existing theoretical views on syntactic complexity.

Beginning L2 complexity development in CLIL and non-CLIL secondary education

The present study analyses the impact of a bilingual Content and Language Integrated Learning (CLIL) programme vis-à-vis a regular monolingual programme on the development of different aspects of L2 learners’ linguistic (syntactic, morphological and lexical) complexity. Five pupils enrolled in a Dutch–English CLIL programme in a secondary school in the Netherlands are compared with five peers following the mainstream programme with English as a Foreign Language (EFL) teaching. The longitudinal development of these ten pupils’ linguistic complexity in L2-English is investigated by means of six complexity measures calculated for each of eleven writing tasks collected over a period spanning their first nineteen months of secondary education. Linear mixed models are used to estimate the effects of time and programme type on the pupils’ L2 complexity. The results indicate that both groups of learners significantly increase the complexity of their L2 writing over the course of the study. Surprisingly, only limited effects of programme type (CLIL vs non-CLIL) are found, despite considerable differences in the quantity and quality of instructional exposure to the target language, suggesting that for these pupils increased and more varied instructional exposure to the L2 in the CLIL programme did not lead to significantly different L2 productions in terms of linguistic complexity. Several possible explanations for these findings are considered and the implications for CLIL research are discussed.

Differential contribution of oral and written modes to lexical, syntactic and propositional complexity in L2 performance in instructed contexts

Complexity of L2 output during oral or written task performance has been associated with the process of restructuring; that is, a qualitative change of the internal L2 system by which interlanguage becomes more elaborate and more efficient in communication. While online pressures may restrain the occurrence of restructuring in oral production, the availability of time and visibility of output in writing might create optimal conditions to deploy more complex linguistic structures, with the concomitant interlanguage development. To test these claims, we conducted a study in which we explored if and how the manifestation of lexical, syntactic and propositional L2 complexity was moderated by the mode in which the task was performed. Our participants were 290 instructed L2 learners. They performed orally and in writing a narrative video-retelling task. The analysis revealed moderating task-modality effects on L2 complexity. We found that the written texts displayed higher scores on all the sub-dimensions of syntactic and lexical complexity. Differences were also observed in the way speakers and writers conveyed the propositional content of the task. We interpret these findings as evidence of the facilitating conditions for restructuring during written production in instructed settings and, accordingly, of the language-learning-potential of L2 writing tasks.