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To improve the application of surfactants and polymers, the knowledge of the interaction of surfactant with polymer is essential. Therefore, the interaction of bovine serum albumin (BSA) with a typical cationic surfactant, tetradecyltrimethylammonium bromide (TTAB) was investigated using the conductivity measurement method in aq. alcohols solutions having numerous alcohols concentrations at definite temperature (310.55K) and the same alcohols concentration at variable temperatures (300.55–323.55K). The types and extent of interactions between BSA and TTAB have been detected from the variation of critical micelle concentration (CMC) for the studied system. The CMC has been achieved from the plots of conductivity against TTAB concentration. One CMC was achieved for the TTAB+BSA mixture in all aq. alcohols media. The CMC values experience a change with the variation of alcohol contents and temperature of the study medium. The extent of micelle ionization (α), counter ions binding (β), and thermodynamic variables such as free energy ( \\( G_m^0 \\)), enthalpy ( \\( H_m^0 \\)) and entropy ( \\( S_m^0 \\)) of micellization were computed from the standard thermodynamic formulae and demonstrated in detail. The \\( G_m^0 \\) values were found negative which pointed out the spontaneous attitude of the aggregation process. Here, the intrinsic enthalpy gain ( \\( H_m^0, \\)) and the compensation temperature (Tc) were also evaluated and explained. The estimated parameters reveal the presence of interaction among the studied components which is dependent on solvent composition and temperature.

[Os 3 (CO) 10 (NCMe) 2 ] reacts with pyrrolidine in refluxing benzene to give the known clusters [HOs 3 (CO) 10 (µ,κ 1 -NCH 2 CH 2 CH 2 CH 2 )] ( 1 ) and [HOs 3 (CO) 10 (µ,η 1 ,κ 1 -C=NCH 2 CH 2 CH 2 )] ( 2 ), in addition to the new triosmium cluster [HOs 3 (CO) 9 (µ,κ 2 -N=C(CH 3 )C=NCH 2 CH 2 CH 2 )] ( 5 ), whose ancillary heterocyclic ligand is formed by C–C coupling involving the nitrile carbon of NCCH 3 and the α-carbon of pyrrolidine. Refluxing 2 in n -octane furnishes the known µ 3 -imidoyl cluster [HOs 3 (CO) 9 (µ 3 ,η 1 ,κ 1 -C=NCH 2 CH 2 CH 2 )] ( 4 ) along with the new pentaosmium cluster [H 3 Os 5 (CO) 14 (µ,η 1 ,κ 1 -C=NCH 2 CH 2 CH 2 )] ( 6 ) which exhibits a metallic core based on an edge-bridged tetrahedron. The doubly metalated pyrrolidine ligand ligates one of the apical osmium atoms in the Os 4 tetrahedron and the bridging Os(CO) 3 moiety in 6 . The bonding in clusters 5 and 6 has been investigated by electronic structure calculations. Graphical Abstract

The reactivity of the benzenedithiolate (bdt)-bridged complex [Fe2(CO)6(µ-bdt)] with arsine, stibine and phosphine ligands has been studied. The new mono- and disubstituted complexes [Fe2(CO)5(EPh3)(µ-bdt)] (E = As, 1; E = Sb 3) and [Fe2(CO)4(EPh3)2(µ-bdt)] (E = As, 2; E = Sb, 4) and the previously reported [Fe2(CO)4(PPh2H)2(µ-bdt)] (5) have been prepared by Me3NO-initiated carbonyl substitution reactions of [Fe2(CO)6(µ-bdt)] with appropriate ligands at 80 °C. Spectroscopic and single-crystal X-ray diffraction studies reveal that in all cases the introduced ligands occupy apical coordination site(s) lying trans to the iron–iron bond. Their electrochemistry has been probed by cyclic voltammetry and selected complexes have been tested as proton reduction catalysts. Monosubstituted complexes 1 and 3 show two irreversible reductions at ca. −1.7 V and −2.0 V, respectively, relative to Fc+/Fc, while the disubstituted complexes 2 and 5 show a single irreversible reduction at ca. −2.2 V and −1.84 V, respectively. Complexes 1, 3 and 5 can catalyse electrocatalytic proton reduction in the presence of either p-toluene sulfonic acid (TsOH) or trifluoroacetic acid (CF3CO2H).

Addition of the bulky redox-active diphosphine 1,8-bis(diphenylphosphino)naphthalene (dppn) to [Fe2(CO)6(µ-edt)] (1) (edt = 1,2-ethanedithiolate) affords [Fe2(CO)4(κ2-dppn)(µ-edt)] (3) as the major product, together with small amounts of a P–C bond cleavage product [Fe2(CO)5κ1-PPh2(1-C10H7)(µ-edt)] (2). The redox properties of 3 have been examined by cyclic voltammetry and it has been tested as a proton-reduction catalyst. It undergoes a reversible reduction at E1/2 = −2.18 V and exhibits two overlapping reversible oxidations at E1/2 = −0.08 V and E1/2 = 0.04 V. DFT calculations show that while the Highest Occupied Molecular Orbital (HOMO) is metal-centred (Fe–Fe σ-bonding), the Lowest Unoccupied Molecular Orbital (LUMO) is primarily ligand-based, but also contains an antibonding Fe–Fe contribution, highlighting the redox-active nature of the diphosphine. It is readily protonated upon addition of strong acids and catalyzes the electrochemical reduction of protons at Ep = −2.00 V in the presence of CF3CO2H. The catalytic current indicates that it is one of the most efficient diiron electrocatalysts for the reduction of protons, albeit operating at quite a negative potential.

This study investigates the assembly behaviour and physicochemical parameters of a drug-surfactant mixture comprising tetradecyltrimethylammonium bromide (TTAB) and promazine hydrochloride (PMZ) in water and aq. solutions of monohydroxy organic compounds (ethanol (EtOH), 1-propanol (1-PrOH), and 2-butanol (2-BuOH)) using conductometric method. The interaction between TTAB and PMZ has been characterized with the assessment of physicochemical quantities (critical micelle concentration (CMC), counter ion binding (β) and thermodynamic parameters (standard Gibbs energy (ΔGmo), enthalpy (ΔHmo), and entropy (ΔSmo)). The introduction of PMZ with TTAB surfactant resulted in a reduction of the CMC value and an augmentation of the magnitude of β. The inclusion of alcohols causes the delaying creation of micelles above 5% w/w of all alcohols employed. The enhancement of CMC values was acquired with the increase of temperature for TTAB and PMZ mixture. The micellization of the TTAB + PMZ system was obtained as spontaneous with -ΔGmo values. The observed values of ΔHm0 and ΔSm0 indicate that, the entropy plays the main roles in the assembly of TTAB + PMZ in aq. media, while the association is governed by the joint contribution from enthalpy and entropy in aq. alcohol solutions. The hydrophobic interaction is the key forces of interaction between TTAB and PMZ in water medium, whereas hydrophobic and ion-induced dipole are the probable interaction in aq. alcohol media. The thermodynamic of transfer and entropy enthalpy compensation parameters are computed and described with proper logics.

The study of phase separation of triton X-100 (TX-100) and levofloxacin hemihydrate (LFH) mixture in aqueous solutions of electrolytes has the keen interest due to the enormous applications in pharmaceutical sectors. Levofloxacin hemihydrate is a third-generation antibiotic drug utilized in the prevention of bacterial diseases. Herein, phase separation or cloud point (CP) temperature of TX-100 + LFH in aqueous solutions of simple sodium salts (sodium acetate (NaOAc), sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), sodium chloride (NaCl), and sodium citrate (Na3CTA)) with varying concentration was explored at atmospheric pressure. Herein, CP temperature was recorded by visual assessment. The achieved cloud point (CP) values of TX-100 + LFH system in the attendance of electrolytes were observed to be decreased with the enhancement of electrolytes. Among employed electrolytes, SO42− was the most effective depressor of CP values due to its salting-out effect. The reducing trend in the CP values of TX-100 + LFH with subsequent enhancement of concentration of electrolytes follows the order: CPNa3CTA>CPNa2SO4>CPNa2CO3>CPNaCl>CPNaOAc. The calculated Gibbs free energy (ΔGco) values for the phase separation of TX-100 + LFH system were found to be positive which directed the phase separation process is nonspontaneous. The enthalpy changes (ΔHco) and entropy changes (ΔSco) of clouding were found to be negative at all concentrations of electrolytes and only positive value achieved at high concentration (900.1 mmol kg-1) of Na3CTA. The assessment of entropy-enthalpy compensation was performed and explained with proper clarification.

Surfactants have the application in drug formulation purposes as common excipients. The use of surfactant in the incidence of additives improves the absorption and drug release phenomenon. Herein, the development of the clouding of non-ionic surfactants (NISs), triton X-100 (TX-100), and ceftriaxone sodium (CTS) drug mixture, in the appearance of potassium salts (KCl, K3PO4, KBrO3, K2SO4, and KI), has been studied by the way of cloud point (CP) measurement method. The CPs of the study system suffered a lessening as the quantities of KCl, K3PO4, KBrO3, and K2SO4 increased while the opposite result was observed for KI salt. Aggregation within the associated solution systems may lead to a decline in the corresponding CP. The standard free energy (ΔGc0) values reveal the non-spontaneous cloudy formation of TX-100 + CTS mixture, and non-spontaneity go through a drop with the growing electrolyte concentration. The standard enthalpy (ΔHc0) and standard entropy (ΔSc0) values for phase partitioning of TX-100 + CTS reveal the exothermic interaction in the presence of KCl, K3PO4, KBrO3, and K2SO4 while mainly hydrophobic in the presence of KI salt. The intrinsic enthalpy (ΔHc0,∗) values reveal that TX-100 + CTS mixture experiences the highest stability in K3PO4 salt media.

Herein, interactions between cetylpyridinium chloride (CPC) and ceftriaxone sodium (CTS) were investigated applying conductivity technique. Impacts of the nature of additives (e.g. electrolytes or hydrotrope (HDT)), change of temperatures (from 298.15 to 323.15  K ), and concentration variation of CTS/additives were assessed on the micellization of CPC + CTS mixture. The conductometric analysis of critical micelle concentration (CMC) with respect to the concentration reveals that the CMC values were increased with the increase in CTS concentration. In terms of using different mediums, CMC did not differ much with the increase in electrolyte salt (NaCl, Na 2 SO 4 ) concentration, but increased significantly with the rise of HDT (NaBenz) amount. In the presence of electrolyte, CMC showed a gentle increment with temperature, while the HDT showed the opposite trend. Obtained result was further correlated with conventional thermodynamic relationship, where standard Gibb’s free energy change ( Δ G m o ) , change of enthalpy ( Δ H m o ) , and change of entropy ( Δ S m o ) were utilized to investigate. The Δ G m o values were negative for all the mixed systems studied indicating that the micellization process was spontaneous. Finally, the stability of micellization was studied by estimating the intrinsic enthalpy gain ( Δ H m o , ∗ ) and compensation temperature ( T c ). Here, CPC + CTS mixed system showed more stability in Na 2 SO 4 medium than the NaCl, while in NaBenz exhibited the lowest stability.

AbstractThe electrochemistry of dppm-bridged dithiolate complexes [M2(CO)4(μ-dppm)μ-S(CH2)nS] (M = Fe, Ru; n = 2, 3) has been studied by cyclic voltammetry. The diiron complexes show similar electrochemical responses in CH2Cl2 but differ significantly in MeCN, while the diruthenium complexes change only slightly with changes in the dithiolate backbone and solvent. Proton-reduction studies in MeCN with HBF4·Et2O as the proton source show that all are active catalysts for proton reduction in their singly reduced state. An additional catalytic event is observed for all, resulting from their partial protonation giving [M2(CO)4(μ-dppm)μ-S(CH2)nS(μ-H)][BF4]. The diiron complexes show better long-term stability to acids, the diruthenium complexes degrading at high acid concentrations.Graphical AbstractThe electrochemical response of dithiolate complexes [M2(CO)4(μ-dppm)μ-S(CH2)nS] (M = Fe, Ru; n = 2, 3) has been investigated in different solvents as well as they have been tested as electrocatalysts for the reduction of protons to hydrogen.