Correlation of thermochemical measurements and quantum chemical calculations of thermally unduced structural transformations of polynuclear complexes [(en)(H2O)3Ni-(pyr)-Ni(H2O)3(en)] 4H2O and [Cd(N-Boc-gly)2(H2O)2]n.

Ispitana je termička stabilnost i mehanizam stupnjevitog razlaganja polinuklearnih kompleksa [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O i [Cd(N - Boc - gly)2(H2O)2]n u temperaturskom intervalu od 320 do 760 K. Utvrđeno je da su svi stupnjevi termički aktivirani. Iz površine endotermnih pikova određene su entalpije procesa, a primenom Kissinger-ove metode određena je ukupna vrednost prividne energije aktivacije svakog stupnja razlaganja. Analiza izotermalnih merenja kompleksa nikla ukazala je na sve značajniji uticaj difuzije sa napredovanjem reakcije. Utvrđena je zavisnost reakcionog puta od brzine zagrevanja kompleksa. Analizom promene oblika zavisnosti efektivne energije aktivacije od stepena napredovanja utvrđeno je postojanje reverzibilnog stupnja u procesu dehidratacije kompleksa nikla i promena ograničavaju¢eg stupnja uz sve značajniji uticaj difuzije. Porast, a zatim pad prividne enrgije aktivacije tokom dehidratacije kompleksa kadmijuma i stupnja razgradnje kompleksa nikla ukazuje na promenu ograničavaju¢eg stupnja. Neprekidni porast energije aktivacije razlaganja kompleksa kadmijuma ukazuje da se tokom razlaganjana odvijaju dva paralelna procesa. Vibracione frekvencije izračunate za izokinetičke temperature odgovaraju vibracijama Ni - OH2, Cd - OH2 i Cd - O veza, što je kvantnohemijskim proračunima i određeno. Korelacijom eksperimentalno određenih i izra£unatih termodinamičkih i kinetičkih parametara definisani su mehanizami dehidratacionih i stupnjeva razlaganja oba kompleksa. Proračuni su pokazali da se tokom dehidratacije kompleksa nikla odvija polimerizacija. Pri malim brzinama, polimerizacija pospešuje izlazak vode iz sistema, dok se pri višim brzinama zagrevanja ovaj proces odvija znatno sporije. Ovo uzrokuje postojanje dva reakciona puta na različitim brzinama zagrevanja. Na osnovu proračuna izračunata je konstanta ravnoteže povratnog stupnja na različitim temperaturama tokom dehidratacije polaznog kompleksa. Na ovaj način je pokazano da gubitak kristalne vode pospešuje odlazak koordinovane vode iz sistema. Pokazano je da niža energija aktivacije razlaganja kompleksa kadmijuma na početku procesa odgovara premeštanju (N - Boc - gly) liganda iz unutrašnjosti sistema ka površini, dok viša odgovara njegovom otkidanju sa same površine.Thermal stability and degradation mechanism of [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O and [Cd(N - Boc - gly)2(H2O)2]n coordination polymers was investigated in 320-760 K temperature range. It was determined that all of the individual steps are thermally activated. Overall enthalpies of these processes were determined from the area of corresponding endothermic peaks, while the overall average value of activation energies of individual degradation processes were determined using the Kissinger method. The thermal degradation starts with multi-step dehydration process, which exhibits increased influence of diffusion on the reaction mechanism during the progress of the reaction, and its reaction path depends on the heating rate. Analysis of dependence of the value of the effective apparent activation energy on the reaction conversion degree indicates the existence of a reversible step in the dehydration process of Ni-coordination polymer and a change of rate-limiting step of this reaction, probably due to diffusion. Increase and then decrease in the value of the effective apparent activation energy for dehydration reaction of Cd-coordination polymer and degradation reaction of Ni-coordination polymer indicates a change of rate-limiting step, likely due to diffusion of released products. Continuous increase in the value of the effective apparent activation energy for degradation reaction of Cd-coordination polymer indicates that the reaction mechanism consists of two parallel processes. Vibrational frequencies corresponding to the determined values of isokinetic temperatures correspond to Ni - OH2,Cd - OH2 and Cd - O bonds, respectively, and this was confirmed using quantum-chemical calculations. Correlation of experimental and calculated thermodynamic and kinetic parameters has allowed the formulation of the corresponding mechanisms of thermal dehydration and degradation for both of these coordination polymers. DFT calculations indicate that Ni-coordination polymer undergoes polymerization during the dehydration process. At low heating rates, polymerization promotes release of water, while at higher heating rates the polymerization is much slower, resulting in two distinct reaction paths at different heating rates. DFT calculations were used to calculate the equilibrium constant of the reversible step of dehydration of Ni-coordination polymer, indicating that the release of uncoordinated water molecules promotes subsequent release of coordinated water molecules. The lower value of activation energy of thermal degradation of Cd-coordination polymer at the beginning of the process corresponds to the transfer of (N - Boc - gly) ligand from the bulk to the surface, while the higher value of activation energy at the end of process corresponds to release of (N - Boc - gl) ligand from the surface

Determination of risk factors for idiopathic anterior knee pain in adolescents

Uvod. Kod pacijenata sa bolom u kolenu se često nakon evaluacije isključi anatomska malformacija, patelofemoralna nestabilnost, sindrom preopterećenja kolena ili neki drugi patološki entitet. Ranije su ovakvi pacijenti tretirani pod dijagnozom hondromalacije patele, dok se u poslednje vreme sve više koristi termin idiopatskog bola u kolenu (IBK). Kao i kod drugih idiopatskih stanja, dijagnoza se postavlja metodom isključivanja patoloških supstrata. Incidenca IBK je visoka i iznosi oko 22/1000, dva puta ćešća u osoba ženskog pola. Uzrok nastanka IBK je višestruk a pravi razlog i dalje ostaje nepoznanica. Poznavanje anatomije zgloba kolena je osnova za razumevanje patogeneze IBK koji se definiše kao stanje bola nastalo usled preopterećenja i preterane fizičke aktivnosti. Bol u kolenu može da nastane kao posledica dejstva spoljašnjih i unutrašnjih faktora, ili njihovom meĎusobnom kombinacijom. IBK se može javiti kod dve potpuno različite grupe pacijenata. Prvu grupu čine mlaĎi, aktivni sportisti kod kojih bol nastaje usled preopterećenja sportom. Drugu grupu čine gojazni adolescenti koji su fizički neaktivni. Kako bi postavili ispravnu dijagnozu idiopatskog bola u kolenu potreban je pažljiv klinički pregled uz dobro uzetu anamnezu. Metod i ciljevi. Istraživanje je sprovedeno u Institutu za zdravstvenu zaštitu majke i deteta Srbije „dr Vukan Čupić“, u periodu od janura 2013 do juna 2015. godine. Ispitanici ove studije su svi adolescenti uzrasta od 12 do 18 godina koji su se javili na pregled u Institut „dr Vukan Čupić“ zbog bola u kolenu a ispunjavaju kriterijume za uključivanje u istraživanje. Ispitivanu grupu je sačinjavao ukupno 71 pacijent. Kontrolna grupa je bio kontralateralni, zdravi ekstremitet istog pacijenta. Cilj ovog istraživanja i izrade doktorske disertacije su da se ispita povezanost potencijalnih faktora rizika sa pojavom IBK, da utvrdimo značaj kliničkih, morfoloških i funkcionalnih karakteristika donjeg ekstremiteta koji mogu doprineti pojavi IBK kod adolescenata i utvrĎivanje interakcije pojedinih faktora rizika i njihovo aditivno dejstvo na pojavu IBK. Rezultati. Od januara 2013. do decembra 2015. Ispitivali smo ukupno 71 pacijenta na Klinici za dečiju hirurgiju. Uzrast pacijenata je bio od 12 do 18 godina (15.4±1.5). Bol je bio lokalizovan na jednoj nozi, i to na desnoj kod 39 pacijenata (54,93%), dok je bol na levoj nozi dominirao kod 32 pacijenta (45,07%). Ukupno smo ispitivali 41 devojčicu (57,75%) i 30 dečaka (42,25). Kod svih pacijenata u anamnezi postoji podatak o bolu u kolenu koji traje duže od 6 meseci i kod svih je prethodno uraĎena NMR kolena kojim je isključen patološki nalaz...Introduction. Not infrequently, patients with knee pain are given a thorough examination that fails to detect any evidence of an anatomic abnormalities, overuse knee injuries, or patellofemoral instability. Historically, these patients may have been given the diagnosis of chondromalacia patellae; however, more recent authors prefer the term idiopathic anterior knee pain. The incidence of ‘‘anterior knee pain’’ is high and is located at 22/1,000 persons per year. Women are affected more than twice as often as men. The aetiology for anterior knee pain are multifactorial. The causes and mechanisms involved in PFPS may be considered in two groups, extrinsic and intrinsic. Idiopathic anterior knee pain may present itself two clinically distinct groups of patiens. The first one has to do with concerns active, perhaps overly active athletic adolescents with activity-related knee pain. The second group consist of obese adolescents who are physically inactive. A careful physical examination is critical to make an accurate diagnosis of anterior knee pain (AKP). Method. The research was conducted at the Institut for Mother and Child health care of Serbia. The subjects of this study were all adolescents aged 12 to 18 who have visiting a doctor because of the anterior knee pain and meet the criteria for inclusion in the study. The study group consisted of 71 patients. The control group was contralateral, healthy limb same patient. The aims of this study were to (1) investigate the association of potential risk factors the development onset of AKP, (2) to determine the significance of clinical, morphological, and functional characteristics of the lower extremities, which may contribute to AKP in adolescents, and (III) to assess interactions of the individual risk factors along with their additive effect on the occurrence of AKP. Results. From January 2013 to Decembar 2015, 71 patients with idiopathic anterior knee pain were examined at the pediatric surgery clinic. The mean age of the patients was 15.4±1.5 years (range 12 to 18 years). The pain was unilaterals and involved right knee in 39 patients (54,93%) and left knee in 32 patients (45,07%). There were 41 (57,75%) female and 30 (42,25) male persons in the sample. All patients had history of knee pain more then 6 months and all underwent radiography and MRI of the knee joint which excluded knee pathology. Conclusion. Analysis of the data shows that the value Q angle of female patients has a high statistically significant correlation with the appearance of AKP. It was also found that both muscle strength and pattelar mobility excert influence on the incidence of AKP in both, males and females

Hydrogen storage in a layered flexible [Ni2(btc)(en)2]n coordination polymer

[Ni2(btc)(en)2]n coordination polymer exhibits a layered two-dimensional structure with weak interaction between the layers. Correlation of experimental measurements, DFT calculations and molecular simulations demonstrated that its structural features, primarily the inherent flexibility of the layered polymeric structure, lead to improved hydrogen storage performance at room temperature, due to significant enhancement in isosteric heats of hydrogen adsorption. Volumetric measurements of hydrogen adsorption at room temperature show up to 0.3 wt.% hydrogen absorbed at 303 K and 2.63 bar of hydrogen pressure, with isosteric heats of adsorption of about 12.5 kJ mol−1. Predicted performance at room temperature is 1.8 wt.% at 48 bar and 3.5 wt.% at 100 bar, better than both MOF-5 and NU-100, with calculated values of isosteric heats for adsorption of hydrogen in 8–13 kJ mol−1 range at both 77 K and 303 K. Grand canonical Monte Carlo calculations show that this material, at 77 K, exhibits gravimetric hydrogen densities of more than 10 wt.% (up to 8.3 wt.% excess) with the corresponding volumetric density of at least 66 gL−1, which is comparable to MOF-5, but achieved with considerably smaller surface area of about 2500 m2 g−1. This study shows that layered two-dimensional MOFs could be a step towards MOF systems with significantly higher isosteric heats of adsorption, which could provide better room temperature hydrogen storage capabilities.This is the peer reviewed version of the following article: Blagojević, V.A., Lukić, V., Begović, N.N., Maričić, A.M., Minić, D.M., 2016, “Hydrogen storage in a layered flexible [Ni2(btc)(en)2]n coordination polymer”, International Journal of Hydrogen Energy, http://dx.doi.org/10.1016/j.ijhydene.2016.08.20

LEAD, MERCURY AND ARSENIC CONTENT IN SPICES: BLACK, WHITE AND GREEN PEPPER, BLACK CUMIN AND GINGER

In order to evaluate the safety of selected commercial spices brands, concentration of lead, mercury and arsenic, as well as  moisture and mineral contents were analyzed in samples of dried black and white pepper powders, black, white and green peppercorns, black cumin seeds and ginger powder. Lead (Pb), mercury (Hg) and arsenic (As) concentrations in spice samples purchased from local markets in Belgrade were determined, after a microwave digestion of the samples, by atomic absorption spectrometry (AAS), using the graphite furnace AAS technique (Pb), cold vapor AAS technique (Hg) and hydride generation AAS technique (As). Trace levels of Pb, Hg and As in the selected dried spices samples were in the range 0.10 ppm - 0.79 ppm, 0.01 ppm - 0.10 ppm and 0.01 ppm - 0.51 ppm, respectively. The maximum Pb concentration was determined in the sample of ginger and it was 0.79 ppm, the maximum concentration of Hg was 0.10 ppm, determined in green peppercorns samples, while the maximum concentration of As in powdered black pepper sample was 0.51 ppm. The moisture and mineral contents in the different analyzed spices were in the range 1.70-13.10% and 3.40-6.50%, respectively. According to the obtained results, the concentrations of the analyzed toxic elements, as well as the moisture and mineral content in selected spices, were below the maximum permissible limits declared by the national legislations deemed safe for human consumption.SADRŽAJ OLOVA, ŽIVE I ARSENA U ZAČINIMA: CRNI, BELI I ZELENI BIBER, CRNI KIM I ĐUMBIRU ovom radu, u cilju utvrđivanja bezbednosti odabranih komercijalnih začina, analizirane su koncentracije teških metala, kao i sadržaj vlage i ukupnih mineralnih materija, u uzorcima sušenog crnog i belog bibera u prahu, crnog, belog i zelenog bibera u zrnu, semena crnog kima i đumbira u prahu. Koncentracije olova (Pb), žive (Hg) i arsena (As) u uzorcima začina iz lokalnih prodavnica u Beogradu, određene su nakon mikrotalasne digestije atomskom apsorcionom spektrometrijom (AAS), primenom tehnike grafitne peći (Pb), tehnike hladne pare (Hg) i hidridne tehnike (As). Određene koncentracije Pb, Hg i As u uzorcima sušenih začina su u opsegu 0,10 ppm - 0,79 ppm, 0,01 ppm - 0,10 ppm i 0,01 ppm - 0,51 ppm, redom. Maksimalna koncentracija Pb od 0,79 ppm određena je u uzorku đumbira, maksimalna koncentracija Hg od 0,10 ppm u uzorcima zelenog bibera u zrnu, dok je maksimalna koncentracija As određena u uzorku crnog bibera u prahu i iznosila je 0,51 ppm. U uzorcima ispitivanih začina sadržaj vlage i mineralnih materija je u opsegu 1,70-13,10% i 3,40-6,50%, redom. Dobijeni rezultati pokazuju da su koncentracije ispitivanih teških metala, kao i sadržaj vlage i mineralnih materija ispod maksimalno dozvoljenih vrednosti propisanih zakonskom regulativom Republike Srbije, kao i da su ispitivani uzorci crnog, belog i zelenog bibera u prahu i zrnu, crnog kima u zrnu i đumbira u prahu propisanog kvaliteta u ovom smislu.HIGHLIGHTSCommercially formulated anti-dandruff shampoos contain zinc pyrithione (ZPT) as an active ingredient that has antifungal, antibacterial and anti-seborrheic effects;In ZPT, pyrithione (PT) forms a complex with a zinc ion in the 2 : 1 ratio;Determination of ZPT concentration in commercial anti-dandruff shampoos by differential pulse polarography was based on an electrochemical reduction of zinc ions in ammoniacal buffer at pH 10.2;Surface active ingredients (anionic and amphoteric) and micro-components in the shampoos did not exert a polarographic interference for the determination of zinc and did not affect the determination of the content of ZPT active ingredient;This simple and sensitive differential pulse polarography method is suitable for a routine and rapid control of the active ingredient content, as well as for the quality control of anti-dandruff shampoos

Probiotic potential of Lactobacillus fermentum G-4 originating from the meconium of newborns

The present study was dedicated to determining probiotic potential of a human isolate G-4, originated from meconium. The isolate was identified using morphological, physiological and biochemical assays and molecular method based on 16S rRNA gene sequencing. In order to evaluate its probiotic properties in vitro tests were performed: the survival in simulated gastrointestinal conditions, adhesion to hexadecane, and antimicrobial activity. Safety aspects of the isolate were examined by testing toxicity, gastrointestinal tolerance and bacterial translocation in vivo, as well as hemolytic activity in vitro. The isolate G-4, identified as Lactobacillus fermentum, showed viability in artificial gastric and intestinal juice (low degree of cell viability reduction for 0.69 and 1.30 logCFU mL(-1) units, respectively), moderate adhesion to hexadecane (39 +/- 2.1 %), and antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype Abony and Clostridium sporogenes, due to production of lactic acid (9.80 g L-1). No signs of toxicity, bacterial translocation, hemolytic activity, were observed

Measles situation in Serbia in an era of measles elimination (2007-2009)

Following the introduction of measles immunization in Serbia in 1971, measles outbreaks were recorded every 3 to 5 years until 1997. The outbreak in 1997 with 4000 cases was the last large outbreak in Serbia. In 2007, an outbreak with 191 laboratory confirmed or epidemiologically linked cases was reported in Vojvodina. In 2008 and 2009, only 3 cases were confirmed. From 2007-2009, measles infections were most frequently detected in the Roma population but also in non-immunized or partially immunized persons from the general population

Determination of risk factors for idiopathic anterior knee pain in adolescents

Uvod. Kod pacijenata sa bolom u kolenu se često nakon evaluacije isključi anatomska malformacija, patelofemoralna nestabilnost, sindrom preopterećenja kolena ili neki drugi patološki entitet. Ranije su ovakvi pacijenti tretirani pod dijagnozom hondromalacije patele, dok se u poslednje vreme sve više koristi termin idiopatskog bola u kolenu (IBK). Kao i kod drugih idiopatskih stanja, dijagnoza se postavlja metodom isključivanja patoloških supstrata. Incidenca IBK je visoka i iznosi oko 22/1000, dva puta ćešća u osoba ženskog pola. Uzrok nastanka IBK je višestruk a pravi razlog i dalje ostaje nepoznanica. Poznavanje anatomije zgloba kolena je osnova za razumevanje patogeneze IBK koji se definiše kao stanje bola nastalo usled preopterećenja i preterane fizičke aktivnosti. Bol u kolenu može da nastane kao posledica dejstva spoljašnjih i unutrašnjih faktora, ili njihovom meĎusobnom kombinacijom. IBK se može javiti kod dve potpuno različite grupe pacijenata. Prvu grupu čine mlaĎi, aktivni sportisti kod kojih bol nastaje usled preopterećenja sportom. Drugu grupu čine gojazni adolescenti koji su fizički neaktivni. Kako bi postavili ispravnu dijagnozu idiopatskog bola u kolenu potreban je pažljiv klinički pregled uz dobro uzetu anamnezu. Metod i ciljevi. Istraživanje je sprovedeno u Institutu za zdravstvenu zaštitu majke i deteta Srbije „dr Vukan Čupić“, u periodu od janura 2013 do juna 2015. godine. Ispitanici ove studije su svi adolescenti uzrasta od 12 do 18 godina koji su se javili na pregled u Institut „dr Vukan Čupić“ zbog bola u kolenu a ispunjavaju kriterijume za uključivanje u istraživanje. Ispitivanu grupu je sačinjavao ukupno 71 pacijent. Kontrolna grupa je bio kontralateralni, zdravi ekstremitet istog pacijenta. Cilj ovog istraživanja i izrade doktorske disertacije su da se ispita povezanost potencijalnih faktora rizika sa pojavom IBK, da utvrdimo značaj kliničkih, morfoloških i funkcionalnih karakteristika donjeg ekstremiteta koji mogu doprineti pojavi IBK kod adolescenata i utvrĎivanje interakcije pojedinih faktora rizika i njihovo aditivno dejstvo na pojavu IBK. Rezultati. Od januara 2013. do decembra 2015. Ispitivali smo ukupno 71 pacijenta na Klinici za dečiju hirurgiju. Uzrast pacijenata je bio od 12 do 18 godina (15.4±1.5). Bol je bio lokalizovan na jednoj nozi, i to na desnoj kod 39 pacijenata (54,93%), dok je bol na levoj nozi dominirao kod 32 pacijenta (45,07%). Ukupno smo ispitivali 41 devojčicu (57,75%) i 30 dečaka (42,25). Kod svih pacijenata u anamnezi postoji podatak o bolu u kolenu koji traje duže od 6 meseci i kod svih je prethodno uraĎena NMR kolena kojim je isključen patološki nalaz...Introduction. Not infrequently, patients with knee pain are given a thorough examination that fails to detect any evidence of an anatomic abnormalities, overuse knee injuries, or patellofemoral instability. Historically, these patients may have been given the diagnosis of chondromalacia patellae; however, more recent authors prefer the term idiopathic anterior knee pain. The incidence of ‘‘anterior knee pain’’ is high and is located at 22/1,000 persons per year. Women are affected more than twice as often as men. The aetiology for anterior knee pain are multifactorial. The causes and mechanisms involved in PFPS may be considered in two groups, extrinsic and intrinsic. Idiopathic anterior knee pain may present itself two clinically distinct groups of patiens. The first one has to do with concerns active, perhaps overly active athletic adolescents with activity-related knee pain. The second group consist of obese adolescents who are physically inactive. A careful physical examination is critical to make an accurate diagnosis of anterior knee pain (AKP). Method. The research was conducted at the Institut for Mother and Child health care of Serbia. The subjects of this study were all adolescents aged 12 to 18 who have visiting a doctor because of the anterior knee pain and meet the criteria for inclusion in the study. The study group consisted of 71 patients. The control group was contralateral, healthy limb same patient. The aims of this study were to (1) investigate the association of potential risk factors the development onset of AKP, (2) to determine the significance of clinical, morphological, and functional characteristics of the lower extremities, which may contribute to AKP in adolescents, and (III) to assess interactions of the individual risk factors along with their additive effect on the occurrence of AKP. Results. From January 2013 to Decembar 2015, 71 patients with idiopathic anterior knee pain were examined at the pediatric surgery clinic. The mean age of the patients was 15.4±1.5 years (range 12 to 18 years). The pain was unilaterals and involved right knee in 39 patients (54,93%) and left knee in 32 patients (45,07%). There were 41 (57,75%) female and 30 (42,25) male persons in the sample. All patients had history of knee pain more then 6 months and all underwent radiography and MRI of the knee joint which excluded knee pathology. Conclusion. Analysis of the data shows that the value Q angle of female patients has a high statistically significant correlation with the appearance of AKP. It was also found that both muscle strength and pattelar mobility excert influence on the incidence of AKP in both, males and females

On Ability of Troubleshooting by Observing Some Physical Layer Parameters of xDSL Transceivers

This article presents a review of the investigation of the possibility of increasing the efficiency of existing line test solutions for troubleshooting testing for IPTV over xDSL, by the results of experimental research on real system under commercial exploitation. At the beginning of this article the main weaknesses of the existing troubleshooting testing are described. In the continuation of the article the physical layer parameters of xDSL transceiver are listed. This article also provides a few specific examples of xDSL lines with their physical layer parameters of xDSL transceivers followed by analysis how they can be used for the purposes of more efficient measurement of parameters of copper pairs

DNA architecture and transcriptional regulation of the Escherichia coli penicillin amidase (pac) gene

The transcriptional regulation of Escherichia coli ATCC11105 penicillin amidase (pac) gene was studied by modifying DNA sequences responsible For promoter activation by cyclic AMP receptor protein (CRP). The nucleotide sequence of the 5'-flanking region of the pac gene contains putative tandem CRP binding sites positioned at -69/-70 and at -111/-112 with respect to the transcriptional start site. Our results obtained with either point mutations or insertion or deletion mutants (each of which rotated the helix structure at the CRP binding site one-half turn) showed significant decrease of penicillin amidase (PA) activity, suggesting the CRP as a major activator. In this study, the evidence fur the importance of spacing between tandem binding sites for CRP as well as for their location related to the promoter core sequence has been provided. Involvement of integration host factor (IHF) as an additional regulatory protein in the pac gene transcription regulation was also analyzed. It is shown that activation of the pac gene transcription is elevated by IHF

Thermal stability and degradation of binuclear hexaaqua-bis(ethylenediamine)-(μ 2-pyromellitato)dinickel(II) tetrahydrate

Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni2(en)2(H2O)6(pyr)]·4H2O, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser–Suzuki function. The obtained individual steps were described by Johnson–Mehl–Avrami A2 model and Šesták–Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products