Labilizing Effect Research Articles

Emotion-related Processes Between Parents and Adolescents: Evidence for Bidirectional Effects over Time

Parent emotion socialization has long been studied in relation to children’s socioemotional adjustment. Little attention has been paid to how parents’ socialization responses are shaped by youth characteristics over time, such as emotional lability. The present study explored the mutual influence between parent emotion socialization and adolescent emotional lability. Participants were 87 adolescents (M = 14.23 years old, SD = .50; 50 girls) and their parents, who completed questionnaires at three time points from 8th grade through 10th grade. Hierarchical linear modeling demonstrated mutual influences between parent emotion socialization and adolescent emotional lability, with relations moderated by adolescent gender. Increases in parents’ reward of negative emotion predicted decreased emotional lability in girls. Parents’ increased magnification of negative emotions corresponded to decreased emotional lability in boys. Boys’ increases in emotional lability predicted decreased parental magnification of negative emotions over time. Increases in parents’ magnification of negative emotions predicted increased emotional lability in girls. Girls’ increases in emotional lability corresponded to increased parental magnification over time. There were no longitudinal effects of adolescent emotional lability on parents’ reward, override, and punishment of negative emotions. Future directions and clinical applications are discussed.

Labile and recalcitrant carbon inputs differ in their effects on microbial phosphorus transformation in a flooded paddy soil with rice (Oryza sativa L.)

Organic carbon (C) can greatly affect soil microbial activity and thus alter the nutrient availability in soil. However, little is known about the microbial-mediated P transformation processes with organic C inputs in flooded soils. This study used high-throughput sequencing technology to investigate the effects of labile (glucose) and recalcitrant (lignin) organic C inputs on P availability and microbial communities in the bulk and rhizosphere soil under rice growth, aiming to clarify the key microorganisms involved in soil P transformation. Glucose addition enhanced microbial P immobilization and decreased P availability in the rhizosphere soil, while lignin amendment increased available P concentration in bulk soil through increased soil pH and altered bacterial community. Organic C inputs stimulated the growth and cooperation of specific P-solubilizing bacteria (e.g., Acetobacter and Phenylobacterium), facilitating the transformation of non-labile P to labile P in bulk soils, but also stimulated the growth of Clostridium_sensu_stricto, immobilizing labile P into their biomass. Irrespective of C supply, soil P availability was correlated positively with the abundances of Phenylobacterium and Desulfosporosinus but negatively with those of Acetobacter, Clostridium_sensu_stricto, Clostridium_IV, Gluconacetobacter and Syntrophomonas. This study emphasized the contrasting effects of labile and recalcitrant C on microbial mechanisms of P transformation in a flooded paddy soil. These findings provide potential strategies for microbially mediated P management in paddy fields.

Organic matter lability modifies the vertical structure of methane-related microbial communities in lake sediments.

Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH4) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiency in sediments. However, the effect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at five profundal stations of an oligo-mesotrophic, boreal lake (Lake Pääjärvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs (Candidatus Methylomirabilis) relative to aerobic methanotrophs (Methylococcales) in the methane oxidation layer of sediment surface decreased, suggesting that Methylococcales were more competitive than Ca. Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially Ca. Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affecting the redox zonation of sediments, significantly modifies the methane producing and consuming microbial community of lake sediments. IMPORTANCE Lakes are important natural emitters of the greenhouse gas methane (CH4). It has been shown that eutrophication, via increasing the input of labile organic matter (OM) into lake sediments and subsequently affecting the redox conditions, increases methane emissions from lake sediments through increased sediment methane production rates and decreased methane oxidation efficiency. However, the effect of organic matter lability on the structure of the methane-related microbial communities of lake sediments is not known. In this study, we show that, besides the activity, also the structure of lake sediment methane producing and consuming microbial community is significantly affected by changes in the sediment organic matter lability.

How biogenic polymers control surfactant dynamics in the surface microlayer: insights from a coastal Baltic Sea study

Abstract. Surfactants can hamper gas exchange by up to 50 % in coastal seas; however, their small-scale temporal and spatial dynamics are poorly constrained. This study investigated possible biogenic sources of surfactants in the sea surface microlayer (SML) and the underlying water at a coastal Baltic Sea site. To relate surfactant dynamics to biogenic production, we conducted two field studies (June and September 2018) and focused on amino acids and carbohydrates as the main components of organic matter derived from phytoplankton. Furthermore the composition of the biochemicals provided insights into microbial degradation dynamics and was complemented by flow-cytometry-based community analysis. In total, 76 samples were collected within an area of approximately 50 km2, allowing for high spatial resolution. Moreover, morning and afternoon sampling enabled us to investigate diel cycles. Our results reveal that surfactant concentrations were tightly coupled to the abundance of nano-phytoplankton and generally higher in September than in June, with cell abundance 3 times higher. Surfactant concentration in June was best explained by the combined effect of the particulate fraction of the non-essential amino acid serine, the concentration of particulate combined carbohydrates (PCHO), and dissolved organic carbon (DOC). Surfactant and PCHO concentrations were significantly enriched in the SML and followed a pronounced diel cycle, possibly linked to microbial processing and/or photo-processing. In contrast to June, the surfactant pool in September correlated to a diverse mixture of semi-labile organic matter components, represented best by dissolved glucose and the essential amino acid isoleucine. We conclude that the surfactant pool in surface seawater is mainly composed of organic matter components that resist rapid microbial degradation. Elevated surfactant concentrations are triggered by the release of fresh organic matter. While the effect of the resistant but less surface-active stock is potentially longer-lasting, the additive effect of labile, highly surface-active agents on gas exchange may diminish on short timescales.

Labile Carbon Input and Temperature Effects on Soil Organic Matter Turnover in Subtropical Forests

Labile Carbon Input and Temperature Effects on Soil Organic Matter Turnover in Subtropical Forests

The Effect of Anxiety Attachment and Avoidance Attachment on Social Anxiety: Mediating Effect of Self-Esteem Lability

The Effect of Anxiety Attachment and Avoidance Attachment on Social Anxiety: Mediating Effect of Self-Esteem Lability

Ability to tolerate distress moderates the indirect relationship between emotion regulation difficulties and loss-of-control over eating via affective lability

IntroductionLoss-of-control eating (LOCE), inability to refrain from or cease eating, may contribute to significant distress and dysfunction, yet research is lacking specificity on vulnerabilities contributing to LOCE as an independent construct. Preliminary evidence indicates potential roles of distress tolerance, emotion regulation, and affective lability, but the relationship between these variables and LOCE has been under-assessed. Material and methodsA sample (N = 3968) consisting of university students completed an assessment of pathological eating and affiliated affective vulnerabilities. A latent variable structural equation model (SEM) was generated to predict LOCE by way of affective lability and indirectly, emotion regulation difficulties and low distress tolerance, controlling for general eating pathology. ResultsFindings indicated a significant direct effect of affective lability on LOCE, as well as significant indirect effects of emotion regulation difficulties and distress tolerance on LOCE, via affect lability. Additionally, distress tolerance moderated the relationship between emotion regulation difficulties and affective lability, such that lower ability to tolerate distress strengthened the relationship and higher distress tolerance capability attenuated it. DiscussionFindings suggest an influence of distress tolerance on the relationship between poor emotion regulation and affective lability, which in turn may affect LOCE. Clinical implications and suggestions for future research are discussed.

The interaction between affective lability and eating expectancies predicts binge eating

ABSTRACT Both affective lability and eating expectancies have been found to predict binge eating. There is the additional possibility that the joint effect of affective lability and eating expectancies incurs further risk: perhaps expectancies for affective relief from eating operate more strongly in those experiencing frequent, rapid shifts in emotion. In the current study, we tested whether such a joint effect predicts binge eating prospectively in college students. We assessed affective lability, eating expectancies, and binge eating in 358 college students at two time points during the first year of college (e.g., December and April). The interaction of affective lability and eating expectancies in December predicted binge eating 4 months later in April. The influence of eating expectancies on binge eating was stronger at higher levels of affective lability. Findings offer support to the hypothesis that risk factors may transact to further elevate risk for eating disorder behaviors. Clinical implications The interaction of affective lability and eating expectancies predicts binge eating Risk factors may interact to further increase binge eating Identification of co-occurring risk factors may have vital treatment implications

Influence of Algal Production and Decomposition on the Carbon Isotope Signature of Labile Particulate Organic Matter on a Productive Continental Shelf Under the Stress of Coastal Hypoxia

To better understand the sources and recycling of labile organic matter in coastal water, we studied the carbon isotope signature of particulate organic carbon (POC) and particulate amino acids, a major group of labile organic compounds, on the shelf of the northern South China Sea. In addition, we were able to compare effects of hypoxia on labile organic matter at one station on the shelf. We found that carbon-weighted average d13C values of particulate amino acids (wAAd13C) were generally higher at more productive offshore stations than nearshore stations. This amino acid d13C distribution suggests that the labile fraction of organic matter in coastal water originated primarily from local primary production. In contrast, bulk POC d13C values showed little spatial variation on the NSCS shelf. The different patterns of wAAd13C and PO13C distributions indicate a combined effect of POM lability and physical processes on the isotopic distribution of organic materials on this productive shelf. Moreover, the amino acid d13C in coastal hypoxic water suggests local primary production as the most likely source of labile organic matter that drives hypoxia on the NSCS shelf. No clear difference was observed in particulate amino acid d13C distribution between hypoxic and oxic waters,

Youth Internalizing Problems and Changes in Parent-Child Relationships Across Early Adolescence: Lability and Developmental Trends.

Few longitudinal studies examine how changes in parent-child relationships are associated with changes in youth internalizing problems. In this longitudinal study, we investigated how developmental trends (linear change) and year-to-year lability (within-person fluctuations) in parental warmth and hostility across Grade 6-8 predict youth internalizing problems in Grade 9 (N = 618) and whether these linkages differ for boys and girls. Developmental trends (greater decreases in warmth, increases in hostility) were associated with more youth internalizing problems. Greater year-to-year lability (more fluctuations) in father hostility and warmth were also associated with more internalizing problems. Greater lability in mother warmth was associated with more internalizing problems for girls only. The strongest effects of lability on internalizing problems were found for youth with the highest lability scores. This study underscores the importance of differentiating developmental trends from lability in parent-child relationships, both of which may be important for youth internalizing problems.

Influence of xylene on the dielectric response of an organoclay‐containing nanocomposite

The dielectric effect, investigated using dielectric spectroscopy and DC dielectric breakdown strength measurements, of introducing xylene into a composite system containing polyethylene, a co-polymer of ethylene and vinyl acetate and an organoclay can be understood in light of X-ray diffraction data. In dielectric spectroscopy, although organoclay alone changes the dielectric response of the polymer blend and xylene has no effect on the unfilled polymer blend, when both xylene and organoclay are present, a synergistic response is revealed at the 1 Vrms amplitude voltage used to acquire the dielectric data. In contrast to this, in DC, dielectric breakdown strength measurements revealed that, under high field conditions, both the xylene and organoclay, independently, caused a decreased breakdown strength. This work was undertaken in order to examine the generality of the possible effects of labile, low molar mass impurities on electrical properties of comparable systems, which may be processed through solvent-based routes.

High Performance Size Exclusion Chromatography-Inductively Coupled Plasma-Mass Spectrometry to Study the Copper and Cadmium Complexation with Humic Acids.

Dissolved organic matter (DOM) plays an important role in the environment by influencing the transport and distribution of organic and inorganic components through different processes: the retention, mobilization, and bio-availability of potentially toxic elements (PTEs). The aim of the present study is to examine the dimensional characterization of humic acids (HA) extracted from soil matrix, as well as to analyze the metal distribution among different ligand classes. The molecular size distribution of the HA extract from soil showed three dimensional classes: 52 KDa, 4.5 KDa, and 900 Da. HPSEC-ICP-MS measurements demonstrated that the dimensional classes, relative to first two fractions, bind the largest part of metals. The complexing capacity of HA was evaluated to assess the pollutants mobility in the environmental system. In particular, cadmium (Cd) and copper (Cu) complexation was investigated due to the great concern regarding their bio-availability and toxicity in natural waters. The complexing capacity of HA solution (20 mg/L) was measured by titration using a high-performance size exclusion chromatography (HP-SEC) coupled to an inductively coupled mass spectrometry (ICP-MS). Results obtained by this technique are compared with those obtained by anodic stripping voltammetry (ASV) to investigate the effects of kinetic lability of complexes on measurements carried by HPSEC-ICP-MS. In this study, results of ligand concentrations and stability constants obtained via the two techniques are assessed considering the detection window associated to the applied analytical methodology. Results obtained using the two analytical techniques showed that Cd is complexed by two classes of ligands. However, the ligand concentration values obtained using the two techniques are different, because the detection window associated to the two methodologies; the complexing capacity, which was obtained as sum of the two classes of ligands, were 33 nmol/L and 9 nmol/L for ASV and HPSEC-ICP-MS, respectively. The copper complexing capacities determined by the two methodologies are comparable: 166 and 139 nmol/L for ASV and HPSEC-ICP-MS, respectively. However, the results of Cu titration differ for the two techniques, highlighting only one class of ligands when ASV was used, and two classes when HPSEC-ICP-MS was employed. Differences on results obtained by the two techniques are explained considering the kinetic lability of complexes; the results show that, differently from previous studies, also Cu complexes can be kinetically labile, if one technique with high reaction time is used, as well some cadmium complexes are sufficient stable to be determined by HPSEC-ICP-MS.

The effects of emotional lability, mind wandering and sleep quality on ADHD symptom severity in adults with ADHD

Mind wandering, emotional lability and sleep quality are currently mostly independently investigated but are all interlinked and play a major role is adult attention-deficit/ hyperactivity disorder (ADHD). Emotional lability is a core feature of the disorder, excessive mind wandering has recently been linked to symptoms and impairments of ADHD and poor sleep quality is experienced by a clear majority of adults with ADHD. All three phenomena lead to functional impairment in ADHD, however their relationship to each other and to ADHD symptom severity is not well understood. Here we used serial multiple mediation models to examine the influence of mind wandering, sleep quality and emotional lability on ADHD symptom severity. 81 adults diagnosed with ADHD participated in this study. We found that mind wandering and emotional lability predicted ADHD symptom severity and that mind wandering, emotional lability and sleep quality were all linked and significantly contributed to the symptomatology of adult ADHD. Mind wandering was found to lead to emotional lability which in turn lead to ADHD symptom severity; and poor sleep quality was found to exacerbate mind wandering leading to ADHD symptoms. Future research should employ objective on-task measures of mind wandering, sleepiness and emotional lability to investigate the neural basis of these impairing deficits in ADHD.

Abstract 3968: Bacterial heat labile enterotoxin LT-IIc effects autophagy and cell death in human TNBC

Abstract Microbes and microbial products are being re-evaluated as potential therapeutic agents for breast cancer treatment. We previously observed the rapid induction of cell death in the mouse TNBC cell line 4T1, and mesenchymal TM12T, but not epithelioid TM12 cells, upon exposure to LT-IIc, a member of the bacterial type II subfamily of ADP-ribosylating toxins that bind to specific ganglioside subtypes. To test the hypothesis that LT-IIc may be effective against human breast cancer, we tested a panel of human breast cancer cells. LT-IIc exposure induced cytotoxicity in TNBC, particularly basal B (mesenchymal) TNBC (BT549 and MDA-MB-231), in a dose dependent fashion. The triple negative non-transformed breast epithelial line MCF10A was unaffected. Two ER+ cell lines (T47D and MCF7), and HER2 overexpressing SKBR3 cells showed limited cytotoxic response. We observed a distinctive rapid accumulation of large cytoplasmic vacuoles in TNBC, but not other normal or transformed cell lines. Combined cytotoxicity and vacuolization were not induced by cholera toxin, LT-IIa holotoxin, or forskolin, but still occurred upon treatment with the LT-IIc isolated B pentamer (which lacks the toxin's catalytic A subunit), suggesting that the effects of LT-IIc were not due to intoxification of the adenylate cyclase pathway. These vacuoles were not intracellular lipid droplets, as determined by lack of staining with Oil Red O. Instead, vacuoles were positive for punctate staining with LC3B, a marker of autophagosome formation. Western blotting of MDA-MB-231 and BT549 cells revealed an increase in LC3B and p62 (sequestosome), a marker of autophagic flux. Bafilomycin, an inhibitor of lysosomal fusion, augmented the cell death effect of LT-IIc, but blocked the accumulation of distended autophagic vacuoles, suggesting a negative autophagy feedback response to bafilomycin. Both necrosis and apoptosis were activated in response to LT-IIc exposure, as indicated by increased annexin/AAD staining and caspase 3/7 activity. Knockdown of ATG5 by siRNA, although blocking ATG5 expression, did not block LC3B lipidation, cell death or increased caspase 3/7 activity in response to LT-IIc, suggesting a noncanonical autophagic response. These results suggest that LT-IIc binding or signaling may represent a novel target of therapy for TNBC. Current studies are directed towards defining the ganglioside content in LT-IIc sensitive cell lines and identifying potential downstream proteomic targets. Citation Format: Patricia A. Masso-Welch, Sofia Girald Berlingeri, Natalie D. King-Lyons, John C. Hu, Christopher Greene, Lorrie Mandell, Matthew Federowicz, Terry D. Connell, Yasser Heakal. Bacterial heat labile enterotoxin LT-IIc effects autophagy and cell death in human TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3968.

Lability in the parent's hostility and warmth toward their adolescent: Linkages to youth delinquency and substance use.

According to family systems and life course theories, periods of intense change, such as early adolescence, can disrupt stable family systems, leading to changes in family relationships. In this longitudinal study, we investigate 2 types of change in parental hostility and warmth toward their children during early adolescence (Grades 6 to 8)-developmental trends (linear declines) and lability (within-person fluctuations around developmental trends)-and their linkages to youth substance use and delinquency in Grade 9 (N = 618). We also test if the linkages between lability and youth risky behavior are moderated by youth gender. After controlling for between-person differences in level and developmental trends, we find greater lability (more fluctuations) in youth-reported parents' warmth and hostility are associated with greater youth delinquency, tobacco use, and polysubstance use initiation. The associations between youth-reported lability in mother and father hostility and polysubstance use demonstrated an inverted U shape pattern: Moderate levels of lability were associated with higher substance use but very low and high lability was associated with relatively lower rates of substance use. Many of the linkages between lability and youth delinquency were significant for girls but not boys. Fewer effects of lability on youth outcomes were found using parent reports. Developmental trends in parents' warmth and hostility were also associated with youth delinquency. Lability has unique implications for youth adjustment, yet appears to differ by youth outcome, gender, and reporter. The discussion focuses on mechanisms that might link changes in parent-youth warmth and hostility to youth risky behavior. (PsycINFO Database Record

The Characteristics and Age Effects of Emotional Lability in ADHD Children With and Without Oppositional Defiant Disorder

Objective: This study evaluated the concurrent validity of emotional lability (EL) in children with ADHD. Method: A total of 2,015 children with ADHD and 745 typically developed controls (TDCs) were assessed and compared on EL. Results: ADHD participants expressed higher EL scores than TDCs, not influenced by gender or IQ. Higher levels of EL symptoms were found in children with comorbid oppositional defiant disorder (ODD) and with ADHD-combined subtype. Receiver operating characteristic (ROC) analyses showed a strong screening efficacy of EL symptoms on ADHD. The effect of developmental age on EL showed a desisting pattern in TDCs, as opposed to a persisting pattern in ADHD (not influenced by ODD comorbid status). ODD symptoms in ADHD showed an ascending pattern. Conclusion: EL can potentially serve as a sentinel index for the presence of ADHD, especially when the ADHD presentation is atypical. ODD may embody a developmental entity distinct from EL.

P 131 Association between clinical depressive symptomatology and brain arousal regulation in medicated patients with major depression

Background According to the arousal regulation model of affective disorders, typical depressive symptoms like sensation avoidance and withdrawal in depression can partly be explained as an auto-regulatory attempt to counteract a tonically high brain arousal, which has repeatedly been shown in unmedicated patients with Major Depression (MDD). Brain arousal has so far not been studied in medicated MDD patients and it is unclear to what extent depressive symptomatology is associated with brain arousal regulation. The aim of this study was to compare arousal regulation in medicated MDD patients with healthy controls and to investigate the association between self-rated depressive symptomatology and brain arousal regulation. We hypothesized that despite drug treatment depressed patients would still show a hyperstable brain arousal compared to healthy controls and that depressive symptomatology will be positively associated with the stability of brain arousal regulation. Methods Between 2006 and 2014, 130 currently depressed MDD patients treated with a Selective Serotonine Reuptake Inhibitor (SSRI) and 130 age- and sex-matched healthy controls received a 15 min resting EEG. Depressive symptomatology was assessed with the Beck Depression Inventory (BDI; self-assessment) and sleep quality and duration was measured with the “Allgemeiner Schlaffragebogen” (SF-A). Brain arousal was assessed with the Vigilance Algorithm Leipzig (VIGALL), which classifies 1-s EEG segments as one of seven EEG-vigilance sub-stages. Results No difference in the regulation of brain arousal/wakefulness between medicated MDD patients and healthy controls was found. Also, there was neither a clear association between depression severity nor individual items of the BDI and arousal regulation. Conclusion Our results are in line with a recent longitudinal study, showing a less stable arousal regulation in MDD patients after treatment with SSRI, suggesting a labilizing effect of SSRI on brain arousal regulation. Limitations are the retrospective design and the heterogenity of the group with respect to depression severity.

Unexpectedly high degree of anammox and DNRA in seagrass sediments: Description and application of a revised isotope pairing technique

Understanding the magnitude of nitrogen (N) loss and recycling pathways is crucial for coastal N management efforts. However, quantification of denitrification and anammox by a widely-used method, the isotope pairing technique, is challenged when dissimilatory NO3− reduction to NH4+ (DNRA) occurs. In this study, we describe a revised isotope pairing technique that accounts for the influence of DNRA on NO3− reduction (R-IPT-DNRA). The new calculation procedure improves on previous techniques by (1) accounting for N2O production, (2) distinguishing canonical anammox from coupled DNRA-anammox, and (3) including the production of 30N2 by anammox in the quantification of DNRA. This approach avoids the potential for substantial underestimates of anammox rates and overestimates of denitrification rates in systems where DNRA is a significant NO3− reduction pathway. We apply this technique to simultaneously quantify rates of anammox, denitrification, and DNRA in intact sediments adjacent to a seagrass bed in subtropical Australia. The effect of organic carbon lability on NO3− reduction was also addressed by adding detrital sources with differing C:N (phytoplankton- or seagrass-derived). DNRA was the predominant pathway, contributing 49–74% of total NO3− reduction (mean 0.42µmolNm−2h−1). In this high C:N system, DNRA outcompetes denitrification for NO3−, functioning to recycle rather than remove N. Anammox exceeded denitrification (mean 0.18 and 0.04µmolNm−2h−1, respectively) and accounted for 64–86% of N loss, a rare high percentage in shallow coastal environments. Owing to low denitrification activity, N2O production was ∼100-fold lower than in other coastal sediments (mean 7.7nmolNm−2h−1). All NO3− reduction pathways were stimulated by seagrass detritus but not by phytoplankton detritus, suggesting this microbial community is adapted to process organic matter that is typically encountered. The R-IPT-DNRA is widely applicable in other environments where the characterization of co-existing NO3− reduction pathways is desirable.

Specific features of the cis labilization effect in the series of pentacarbonyltechnetium halides

Causes of abnormal (from the viewpoint of traditional views on the cis labilization effect) enhancement of the tendency of pentacarbonyltechnetium halides to decarbonylation in the series I–Br–Cl–F are discussed. Two possible causes are considered: “nonclassical” halogen···cis-C interaction and electrostatic interactions of the halide ligand with the Tc atom in the initial complex and pentacoordinate transition state. Relative stabilization of the transition state due to electrostatic interactions is concluded to be the most probable cause of the observed trend.

Reactivity of higher technetium carbonyls in CO replacement: A quantum chemical analysis

The CO replacement in higher technetium carbonyls (hexacarbonyltechntium cation, pentacarbonyltechnetium halides, and actually existing and hypothetical technetium tetracarbonyl complexes) was analyzed by quantum-chemical calculations. Dissociative and associative mechanisms of the reaction in a vacuum and in solvents were analyzed using the variational transition state theory. The solvent effect on the process was considered within the framework of PCM model and with explicit inclusion of different numbers of solvent molecules. The dissociative pathway was shown to better agree with the experimental data. Higher kinetic stability of the hexacarbonyl cation compared to pentacarbonyl halides and of pentacarbonyl halides compared to related tetracarbonyl complexes is mainly attributable to energetic features of the five-coordinate transition state (cis labilization effect exerted by π-donor ligands), as in related carbonyl complexes of other dmetals. Reactivity trends observed within the series of technetium pentacarbonyl and tetracarbonyl complexes were discussed.