Enthalpy Of Complexation Research Articles

A reversible, benzothiazole-based “Turn-on” fluorescence sensor for selective detection of Zn2+ ions in vitro

Temperature-driven, highly sensitive and selective “TURN-ON” fluorometric detection of Zn2+ by benzothiazole-based probes (L1 and L2) was reported in physiological pH in the present work. Iron(II) acted as the reversible switch or trigger for the reversible detection of Zn2+ ions by the probes resulting in “TURN-OFF” fluorescence at room temperature. However, selective detection of Zn2+ in the presence of Fe2+ was irreversible at 0–5 °C. Such temperature dependence on reversible fluorometric detection of Zn2+ in the presence of Fe2+ was explained from the thermodynamic perspective as well as DFT calculations in which the absolute enthalpy (H) and Gibbs free energy (G) of the resultant complexes and the fluorophores (L1 and L2) at different temperatures were determined. Enhanced fluorescence of the Zn2+ bound probes was due to the inhibition of excited-state intramolecular proton transfer (ESIPT). Effect of solvents, pH, and temperature on the fluorometric detection of Zn2+ was also probed in the present work. The results were translated into the visual detection of Zn2+ on paper-based fluorescence probe and later we demonstrated the sensing of mobile Zn2+ ions by the probes in living HeLa cells as the proof of concept of our present investigations. A benzothiazole-based, “TURN-ON” fluorescent sensor was developed for selective and reversible detection of Zn2+in vitro, in which Fe2+ acted as the reversible switch.

Thermodynamics of Complexation of Sm3+ and Ce3+ Ions with L-Leucine in Aqueous Solution at 298.15 K

The enthalpies of complexation of the Sm3+ and Ce3+ ions with L-leucine at 298.15 K and an ionic strength of 0.5 (KNO3) have been determined by the calorimetric method. The thermodynamic characteristics of complexation of lanthanide ions with amino acids have been calculated. The potentiometric method was used to determine the stability constants of cerium and samarium complexes with the L-leucinate ion at 298.15 K and an ionic strength of 0.5 (KNO3).

Lanthanides(III) and Silver(I) complex formation with triamines in DMSO: The effect of ligand cyclization

The thermodynamic functions of complexation between lanthanides(III) and 1,4,7-triazacyclononane (TACN) together with those of some of the above metal ions with the TACN-linear-analogue,N′-methyl-N′′-(2-(methylamino)ethyl)ethane-1,2-diamine (DMDIEN), are determined in dimethylsulphoxide (DMSO).The study aims to investigate the effect of ligand cyclization and methylation on the stability and nature of the complexes in non-aqueous solution. The stability constants of Ln3+/TACN complexes were obtained by means of potentiometric titrations at 298 K and I = 0.1 mol dm−3, using Ag+ as competitive ion. Ln3+-ligand complexation enthalpies were obtained by calorimetric titrations, extended also to the silver(I)-TACN system, whose thermodynamic data in DMSO are not published. Calorimetry was applied also to obtain simultaneously enthalpy values and stability constants of the Ln3+/DMDIEN systems, for which the difference in stabilities between Ag+ and Ln3+-DMDIEN complexes did not allow the competitive potentiometric method to work.The Ag+ ion forms mono- and poly-nuclear AgiLji+ complexes with TACN (i:j = 1:1, 1:2 and 2:3), whereas all lanthanide ions form with TACN both 1:1 complexes and 1:2, from Tb3+ to Lu3+. Only 1:1 species were detected for the Ln3+-DMDIEN systems. The 1:1 TACN complexes show an extra stability both with respect to those of DIEN and those of the linear analogue DMDIEN. Negative enthalpies favor the formation of all complexes, while entropies partially counteract the complexation. The results for TACN systems are compared with those here obtained for DMDIEN and for DIEN, reported previously. Density Functional Theory (DFT) calculations, carried out in presence of DMSO introduced as implicit solvent, were performed on some of the Ln3+ complexes with TACN and DIEN to provide insights into the structures and related solvation energies of the species formed in solution. Calculations support a tri-dentate coordination of both ligands. The effects of ligand methylation and cyclization on the stability constants, enthalpies and entropies of complex formation are discussed. The thermodynamic and DFT integrated data indicate that the trends of the thermodynamic functions concerning the complexation reactions of lanthanide ions in DMSO depend on the different solvation of the complexes.

Strong N-X⋅⋅⋅O-N Halogen Bonds: A Comprehensive Study on N-Halosaccharin Pyridine N-Oxide Complexes.

A study of the strong N-X⋅⋅⋅- O-N+ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N-halosaccharins and pyridine N-oxides (PyNO). DFT calculations were used to investigate the X⋅⋅⋅O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X⋅⋅⋅O XBs. The XB interaction energies vary from -47.5 to -120.3 kJ mol-1 ; the strongest N-I⋅⋅⋅- O-N+ XBs approaching those of 3-center-4-electron [N-I-N]+ halogen-bonded systems (ca. 160 kJ mol-1 ). 1 H NMR association constants (KXB ) determined in CDCl3 and [D6 ]acetone vary from 2.0×100 to >108 m-1 and correlate well with the calculated donor×acceptor complexation enthalpies found between -38.4 and -77.5 kJ mol-1 . In X-ray crystal structures, the N-iodosaccharin-PyNO complexes manifest short interaction ratios (RXB ) between 0.65-0.67 for the N-I⋅⋅⋅- O-N+ halogen bond.

Strong N−X⋅⋅⋅O−N Halogen Bonds: A Comprehensive Study on N‐Halosaccharin Pyridine N‐Oxide Complexes

AbstractA study of the strong N−X⋅⋅⋅−O−N+ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). DFT calculations were used to investigate the X⋅⋅⋅O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X⋅⋅⋅O XBs. The XB interaction energies vary from −47.5 to −120.3 kJ mol−1; the strongest N−I⋅⋅⋅−O−N+ XBs approaching those of 3‐center‐4‐electron [N−I−N]+ halogen‐bonded systems (ca. 160 kJ mol−1). 1H NMR association constants (KXB) determined in CDCl3 and [D6]acetone vary from 2.0×100 to >108 m−1 and correlate well with the calculated donor×acceptor complexation enthalpies found between −38.4 and −77.5 kJ mol−1. In X‐ray crystal structures, the N‐iodosaccharin‐PyNO complexes manifest short interaction ratios (RXB) between 0.65–0.67 for the N−I⋅⋅⋅−O−N+ halogen bond.

Complexation of Light Trivalent Lanthanides with N-(2-Hydroxyethyl)ethylenediamine-N,N',N'-triacetic Acid in Aqueous Solutions: Thermodynamic Analysis and Coordination Modes.

N-(2-Hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA, denoted as H3L) is a strong chelating ligand that is widely used in the separation of f elements as relevant to the nuclear fuel cycle. There is much to be known about the structure and composition of the coordination sphere of the complexes of HEDTA with lanthanides. The complexation of HEDTA with light lanthanides (La3+, Nd3+, and Eu3+) was investigated thermodynamically and structurally in aqueous solutions. Potentiometry and microcalorimetry were performed to acquire the complexation constants (25-70 °C) and enthalpies (25 °C), respectively, at I = 1.0 mol·L-1 NaClO4. Coordination modes of the complexes were analyzed by luminescence spectroscopy and NMR spectroscopy. The results indicate that there are two successive Ln3+/HEDTA complexes, LnLaq and Ln2(H-1L)22- (Ln3+ refers to La3+, Nd3+, and Eu3+; H-1L4- refers to deprotonation of the hydroxyl group) during titration. The hydroxyl group of HEDTA is coordinated in the Ln3+/HEDTA complex. The dinuclear Ln2(H-1L)22- complex is present as a carboxyl-bridged centrosymmetric dimer, and two carboxyl groups in bridging positions are coordinated to two adjacent Ln3+ cations. Complexation of NdLaq is exothermic, while formation of the hydrolytic complex Nd2(H-1L)22- is endothermic. Both NdLaq and Nd2(H-1L)22- complexes are driven by entropic force. These data will help to predict the behavior of lanthanides in the separation process, where HEDTA is used as the aqueous complexant.

Thermodynamics of Complexation Reactions of Nd3+ and Eu3+ Ions with Glycyl-DL-Alanine, Glycyl-DL-Leucine, and Glycyl-DL-Tyrosine in Aqueous Solution in the pH Range рН 1.6–7.5

The calorimetric enthalpies of complexation of selected dipeptides, namely, glycyl-DL-alanine, glycyl-DL-leucine, and glycyl-DL-tyrosine (HL±), with Nd3+ and Eu3+ ions at 298.15 K and an ionic strength of 0.1 (on the background of KNO3) were determined. Thermodynamic characteristics of formation were calculated for the LnL2+ and LnHL3+ complexes of these dipeptides with Nd3+ and Eu3+ ions for various molar ratios [metal] : [ligand] in the pH range 1.6–7.5. The obtained thermodynamic parameters served to infer the structures of the complexes.

A Fragmenting Protocol with Explicit Hydration for Calculation of Binding Enthalpies of Target-Ligand Complexes at a Quantum Mechanical Level.

Optimization of the enthalpy component of binding thermodynamics of drug candidates is a successful pathway of rational molecular design. However, the large size and missing hydration structure of target-ligand complexes often hinder such optimizations with quantum mechanical (QM) methods. At the same time, QM calculations are often necessitated for proper handling of electronic effects. To overcome the above problems, and help the QM design of new drugs, a protocol is introduced for atomic level determination of hydration structure and extraction of structures of target-ligand complex interfaces. The protocol is a combination of a previously published program MobyWat, an engine for assigning explicit water positions, and Fragmenter, a new tool for optimal fragmentation of protein targets. The protocol fostered a series of fast calculations of ligand binding enthalpies at the semi-empirical QM level. Ligands of diverse chemistry ranging from small aromatic compounds up to a large peptide helix of a molecular weight of 3000 targeting a leukemia protein were selected for systematic investigations. Comparison of various combinations of implicit and explicit water models demonstrated that the presence of accurately predicted explicit water molecules in the complex interface considerably improved the agreement with experimental results. A single scaling factor was derived for conversion of QM reaction heats into binding enthalpy values. The factor links molecular structure with binding thermodynamics via QM calculations. The new protocol and scaling factor will help automated optimization of binding enthalpy in future molecular design projects.

Exploring the Origins of Enthalpy–Entropy Compensation by Calorimetric Studies of Cyclodextrin Complexes

Cyclodextrin complexes were used as simple model systems to explore the enthalpy-entropy compensation phenomenon, which is often observed in biomolecular processes, e.g., in protein-ligand binding. The complexation thermodynamics for the binding of a series of adamantane derivatives to several cyclodextrin hosts were determined by isothermal titration calorimetry in the temperature range 10-55 °C. As for other cyclodextrin complexes, the thermodynamic parameters depended systematically on the structural modifications of the cyclodextrins. Hydroxypropyl chains at the rims of the cyclodextrin hosts changed the thermodynamic fingerprint of binding to all guests by inducing significant increases in the complexation enthalpies and entropies. Similarly, the heat capacity changes upon complexation also showed a linear dependence on the number of hydroxypropyl chains. The altered complexation thermodynamics was ascribed to the increased dehydration of polar groups on the guest by the hydroxypropyl chains on the host. This unfavorable interaction destabilized the complexes as the enthalpic penalty was only partially compensated by the gain in entropy. The degree of enthalpy-entropy compensation depended on the guest molecule and seems to be related to the hydrophilicity/hydrophobicity of the desolvated molecular surface.

Effects of amylose content and enzymatic debranching on the properties of maize starch-glycerol monolaurate complexes

The effects of pullulanase debranching on the properties of maize starch (waxy, normal and high amylose)-glycerol monolaurate (GML) complexes were studied. Pullulanase pretreatment produced more starch chains with favourable lengths (DP ≥ 25) to encourage inclusion complex formation. The debranched starch showed higher amylose content (from 11.2 to 58.6%) than the native starch (from 0.68 to 53.4%). The V-type characteristic diffraction peaks (7.5°, 13.1° and 20.2° 2θ) became more obvious after the starch received the debranching treatment. Thermal properties indicated that the melting enthalpy of the debranched starch-GML complexes (from 6.45 to 10.13 J/g) was higher than those of the untreated complexes (from 0 to 8.91 J/g). The swelling power values and degree of hydrolysis of the starches decreased with the increase in amylose content. In vitro digestibility analysis suggested that the hydrolysis of the starch-GML samples was further restricted by applying the debranching treatment to the starch.

Complexation of Lanthanides with N, N, N', N'-Tetramethylamide Derivatives of Bipyridinedicarboxylic Acid and Phenanthrolinedicarboxylic Acid: Thermodynamics and Coordination Modes.

The thermodynamics of Nd(III) and Eu(III) complexes with N, N, N', N'-tetramethyl-2,2'-bipyridine-6,6'-dicarboxamide (TMBiPDA) and N, N, N', N'-tetramethyl-1,10-phenanthroline-2,9-dicarboxamide (TMPhenDA) in CH3OH/10%(v)H2O solutions were studied. Stability constants and enthalpies of complexation were determined by absorption spectrophotometry, luminescence, and calorimetry. The stability constants of corresponding lanthanide complexes decrease in the order of TMPhenDA > TMBiPDA, while those of the corresponding ligand complexes with lanthanides decrease in the order of Nd(III) > Eu(III). The stepwise reactions for all 1:1 complexes as well as for the 1:2 Nd(III) complexes are driven by both enthalpy and entropy, while those for the 1:2 Eu(III) complexes are driven by entropy. The stronger affinity of TMPhenDA to Nd(III) and Eu(III) than that of TMBiPDA is predominantly arisen from its high preorganization. The spectra of the complexes in solutions are similar, implying that Nd(III) and Eu(III) coordinate with the two ligands in the same mode, which have been validated by 1H and 13C NMR titrations using La(III) as lanthanide tracer. The luminescence lifetimes of the Eu(III) complexes with TMBiPDA and TMPhenDA were evaluated by TRLFS. Structures of Nd(III)/TMPhenDA and Eu(III)/TMPhenDA complexes, identified by single-crystal X-ray diffractometry, show that ligand coordinates to metal in a tetradentate mode via two aromatic N-donors and two amide O-donors, and the central cation (Nd(III) or Eu(III)) is 10-coordinated by two whole TMPhenDA and two solvent (water or methanol) molecules. The M-O bond distances are almost identical, while the Nd-N bond distance is shorter than the Eu-O bond.

Molecular design and engineering for affinity separation processes using isothermal titration calorimetry (ITC) and molecular modeling (MM)

A molecular design approach based on isothermal titration calorimetry (ITC) and molecular modeling (MM) was investigated for the development of new extractants in liquid-liquid extraction (LLX) systems. The molecular designs were validated in LLX experiments. Key in the regeneration of a solvent by temperature-swing back-extraction is the temperature dependency of the complexation equilibrium, which is related to the enthalpy of complexation ∆H. The relation between the molecular structure of extractants and the thermodynamics of complexation in LLX was studied for extraction of acetic acid by basic extractants and 4-cyanopyridine by phenols. For the basic extractants longer alkyl chains and additions of rings decreased ∆H, whereas for the phenols the acidity of the phenolic proton, and hence the complexation enthalpy, could be increased by electron withdrawing substituents.Using ∆H as determined with ITC, the temperature dependency of the liquid-liquid equilibrium could indeed be described. Also enthalpy-entropy compensation (EEC) could be observed in the data obtained by ITC, i.e. for extractants of the same family with a larger enthalpy, an opposite effect on the entropic contribution was observed.

Thermodynamic mechanism of particulation of sodium alginate and chitosan polyelectrolyte complexes as a function of charge ratio and order of addition

This study focused on mechanistic understanding of the effect of charge ratio, order of addition and resulting thermodynamics of interaction on the formation and properties of polyelectrolyte complexes (PECs) from sodium alginate and chitosan at a constant tightly controlled pH 4 where the zeta potential difference was maximum for the formation of PECs. The morphology, particle size and particle size distribution as well as the stability of PECs were investigated as a function of molar charge ratio, and the order of addition. The association binding constant Ka and the stoichiometry of interaction between the two electrolytes, evaluated using Isothermal titration calorimetry, showed that the stoichiometry and enthalpy of reactions were strongly affected by the order of addition and influenced the average particle size and zeta potential of PECs. The addition of alginate (-) into chitosan (+) gave positively charged particles and resulted in stronger interactions characterized by larger enthalpy and entropy of complexation which led to smaller particles. Reversing the order of addition gave negatively charged particles that were larger. Morphologies of complexes studied using scanning electron microscopy (SEM) showed distorted spherical particles for both orders of addition and at most charge ratios. Stability during 8 weeks was found to depend on the order of addition and charge ratio. Alginate in chitosan gave more stable PECs consistent with the thermodynamics of interaction which showed stronger interactions for this order of addition. The particle sizes and size distributions rapidly increased near electrical neutrality during storage at 4 °C where aggregation was facilitated because of electrical neutrality but particles were stable when the net charge was either strongly positive or strongly negative.

Thermodynamics of Complexation Reactions of Pr3+ and Sm3+ Ions with Glycylglycine in an Aqueous Solution

Enthalpies of complexation of diglycine (HL±) with Pr3+ and Sm3+ ions at 303.15 K and I = 0.5 (KNO3) have been determined by means of calorimetry. The thermodynamic parameters of the formation of diglycine complexes with Pr3+ and Sm3+ ions have been calculated at different molar ratios between metal and the ligand.

Thermodynamic study of the complexation of humic acid by calorimetry

Although the thermodynamic quantities (Gibbs free energy, reaction enthalpy, and entropy) of the complexation of humic acid are necessary for the discussion of the reaction thermodynamics, their accurate determination, especially concerning dissolved humic acid in deep groundwater, has not been carried out. In this study, a combination of potentiometry and calorimetry was used for the determination of the thermodynamic values of complexation of typical humic acid and groundwater humic acid, which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe humic acid was independent of the pH of the bulk solution, whereas that of typical humic acid was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe humic acid is negligible because of its relatively small molecular size. In addition, the effect of the heterogeneity of Horonobe humic acid was not significant. Moreover, the complexation enthalpy of Horonobe humic acid was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe humic acid was not affected by the functional group heterogeneity. Consequently, the unique complexation mechanism of Horonobe humic acid was revealed based on the determined thermodynamic quantities. The migration of radionuclides in the deep underground environment must be affected by these characteristics; thus, the accurate determination of thermodynamic quantities of in situ humic substances is very helpful for the safety assessment of geological disposal, when disposal sites for radioactive waste are chosen.

A topological model for predicting adsorption energies of polycyclic aromatic hydrocarbons on late-transition metal surfaces.

We introduce and validate by first-principles calculations an analogy between metal coordination chemistry and the adsorption of polycyclic aromatic hydrocarbons (PAHs) at metal surfaces for the derivation of a model for predicting the PAH adsorption energies. We correlate the binding of PAH on the metal surface with the coordination between metal atom and the ligands in the metal complex, where the formation enthalpy of metal complexes is mainly determined by the strength of a single metal-ligand (M-L) bond and by the number of the M-L bonds. This analogy allows estimation of the adsorption energies only on the basis of the structure of the PAHs and of their adsorption configurations. The adsorption energies of PAHs are found to depend on simple geometric parameters, such as the number of metal-carbon bonds. Moreover, when the lattice of the metal surface is commensurate with the size of benzene rings, the contribution to the adsorption energy from η2-coordination is about twice that from η1-coordination. These results show that the principles of coordination chemistry can facilitate the modeling of processes at metal surfaces, and pave the way to systematically model reactions involving complex adsorbates at surfaces.

Formation of CaUO2(CO3)32- and Ca2UO2(CO3)3(aq) complexes at variable temperatures (10-70 °C).

The ternary complexation of calcium uranyl tricarbonate species, CaUO2(CO3)32- and Ca2UO2(CO3)3(aq), which are the predominant U(vi) complexes in groundwater and seawater, was investigated at variable temperatures from 10 to 70 °C. Time-resolved laser fluorescence spectroscopy (TRLFS), calcium ion-selective electrode potentiometry, and ultraviolet/visible (UV/Vis) absorption spectroscopy were complementarily employed to determine the formation constants (log Kx13, x = 1 and 2 for mono- and dicalcium complexes, respectively). at infinite dilution (zero ionic strength) was determined by correction using specific ion interaction theory (SIT), and an increasing tendency of with temperature was observed. In addition, the molar enthalpy of complexation (ΔrHm) was measured by calorimetry at 25 °C. Based on thermodynamic data obtained in this work, the approximation models were examined for the prediction of the temperature effect on the complexation, and the constant enthalpy approximation with the chemical complexation reaction modified to an isoelectric reaction showed a satisfactory prediction of in the temperature range of 10-70 °C. Finally, the results of U(vi) speciation in groundwater indicated that the dominance of calcium uranyl tricarbonate complexes would be weakened at elevated temperatures by the strongly enhanced hydrolysis of U(vi).

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation.

The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi-method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (log β0, Δr H0m, Δr S0m, Δr G0m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X-ray absorption fine structure spectroscopy complemented with quantum-mechanical ab initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV-vis, laser fluorescence, and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal/malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding log β10 and log β20 of about 6 and 9, respectively. The respective complexation enthalpies Δr H0m,1 and Δr H0m,2 showed average values of 5 kJ·mol-1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation, and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f/5f element homology.

Effects of glycerides with different molecular structures on the properties of maize starch and its film forming capacity

To investigate the effect of glycerides with different molecular structures on the properties of maize starch (MS) and its film forming capacity, the complexing index, swelling power, diffraction patterns and thermograms of MS-glyceride complexes were measured, and the moisture resistance and mechanical properties of MS-based films were studied. The glycerol monolaurate (GML) more strongly interacted with amylose molecules than did glycerol monostearate (GMS) or glycerol tristearate (GTS). The swelling power of MS decreased with the addition of glycerides. X-ray diffraction demonstrated that the diffraction intensities of amylose-lipid inclusion complexes decreased with increasing acyl chain lengths and increased as the number of stearyl chains increased. Addition of glycerides inhibited the gelatinization process of native MS. The melting enthalpies (△H) of amylose-lipid complexes followed the order: GML > GTS > GMS. MS-based film with glycerides showed higher tensile strength values, lower elongation at break values and better moisture resistance than native starch-based film. The composite film with GML showed better mechanical properties and moisture resistance than the composite film with GMS and GTS.

Enzymatic debranching of starches from different botanical sources for complex formation with stearic acid

Starches from different botanical sources (corn, potato, and tapioca) were modified enzymatically using pullulanase, and the resultant debranched starches were used to formulate inclusion complexes with stearic acid. Effects of the debranching and botanical source of starch on the degree of complex formation, thermal and crystalline characteristics of the complexes were analyzed. The amount of stearic acid in the complexes, recovered as precipitates from aqueous reaction mixtures, was high in the order of tapioca, potato and corn starches. By debranching for 12 h, tapioca starch could form the complex with stearic acid at a recovery yield of 71%, which was the maximum among the values obtained with other starches. Further, all the starch/stearic acid complexes exhibited a combination of V- and B-type polymorphs under X-ray diffraction analyses. From a thermal transition analyses, both type I and II crystals were observed in the inclusion complexes. Melting enthalpy of the inclusion complexes improved by debranching, indicating that the complexes were thermally stabilized. Overall data revealed that the enzymatic debranching of starch effectively improves the complexation, crystallinity, dispersion ability and stability of starch-stearic acid complex.