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Low strength and rapid biodegradability of Acellular Dermal Matrix (ADM) restrict wider clinical application as rapid cell delivery platform in situ, for management of burn wounds. Herein, extracted ADM was modified by dual cross-linking approach with ionic crosslinking using chitosan (CTS) and covalent cross-linking using an iodine modified 2, 5-dihydro-2,5-dimethoxy-furan (DHF-I) cross-linker; termed as CsADM-Cl. In addition, inherent growth factors and cytokines were found to be preserved in the CsADM-Cl, irrespective of ionic/covalent crosslinking. CsADM-Cl demonstrated improvement in post crosslinking stiffness with decreased biodegradation rate. This hybrid crosslinked hydrogel supported adhesion, proliferation, and migration of human foreskin derived fibroblasts (HFCs) and keratinocytes (HKC). Also, the angiogenic potential of CsADM-Cl was manifested by chick chorioallantoic membrane (CAM) assay. CsADM-Cl showed excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, CsADM-Cl treated full thickness (FT) burn wounds demonstrated rapid healing marked with superior angiogenesis, well-defined dermal-epidermal junctions (DEJ), mature basket weave collagen deposition, and development of more pronounced secondary appendages. Altogether, the bioactive CsADM-Cl hydrogel established significant clinical potential to support wound healing as an apt injectable antibacterial matrix to encounter unmet challenges concerning critical burn wounds.

The synthesis of two new lead(II) coordination polymers, [Pb 2 (mpic) 4 (H 2 O)]·0.5H 2 O ( 1 ) and [Pb 2 (phen) 2 (cit)(mes)]·2H 2 O ( 2 ) has been reported, where mpic=3-methyl picolinate, phen= o -phenanthroline, H 2 cit=citraconic acid, H 2 mes mesaconic acid. X-ray single crystal diffraction analyses showed that the complexes comprise topologically different 1D polymeric chains stabilized by weak interactions and both containing tetranuclear Pb 4 units connected by carboxylate groups. In compound 1 3-methylpicolinic acid is formed in situ from 3-methyl piconitrile, and mesaconate and citraconate anions were surprisingly formed from itaconic acid during the synthesis of 2. The photoluminescence and thermal properties of the complexes have been studied.

Excited state intramolecular proton transfer (ESIPT) of 2-hydroxy-1-naphthaldehyde semicarbazone (2HNS) has been studied in n-heptane and methanol solvents exploiting absorption, steady state and time-resolved fluorometric techniques. Experimental results reveal that although the intramolecular proton transfer (IPT) reaction does not take place in the ground state (S 0 ), the process is feasible in the lowest excited singlet state (S 1 ). Ab initio quantum chemical calculations have been carried out to judge the feasibility of the IPT process in the different electronic states. Density functional theory (DFT) has been used for the ground state calculations while those relevant to the lowest excited singlet state have been performed exploiting the time dependent density functional theory (TDDFT) using the B3LYP functional at 6-31G** level. The distances of the transferable hydrogen from the oxygen atom (wherefrom it is dislocated during the IPT reaction) as well as the nitrogen atom (to which it gets attached) have been taken as the independent reaction coordinates. The calculations reveal that either of these two parameters may be used to monitor the progress of the prototropic process since both lead to the same prototropic species passing through the same transition state. Simulation of the potential energy curves (PECs) and potential energy surfaces (PESs) leads to visualize the advancement of the reaction. Calculations imply that formation of the tautomer in the S 0 state leads to endothermicity, while the process is exothermic in the S 1 state. The calculated activation energy ( E act ) of the process also decreases in the excited state. Thus, although the reaction is not feasible in the ground state, both the thermodynamic (Δ H ) and the kinetic ( E act ) factors favor the prototropic process to occur in the S 1 state. This article reveals that any of the suitably and logically chosen structural parameters giving the same value of the reaction parameters and resulting in the same transition state may serve as the reaction co-ordinate.

Reaction of the 4-R-benzaldehyde thiosemicarbazones (denoted in general as L-R; R = OCH3, CH3, H, Cl and NO2) with trans-[Pd(PPh3)2Cl2] afforded a group of mixed-ligand complexes (denoted in general as 1-R) incorporating a N,S-coordinated thiosemicarbazone, a triphenylphosphine and a chloride. Similar reaction with Na2[PdCl4] afforded a family of bis-thiosemicarbazone complexes (denoted in general as 2-R), where each ligand is N,S-coordinated. Crystal structures of 1-CH3, 1-NO2, 2-OCH3, 2-NO2 and L-NO2 have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as bidentate N,S-donors forming five-membered chelate rings. With reference to the structure of the uncoordinated thiosemicarbazone, this coordination mode is associated with a conformational change around the C N bond. All the 1-R and 2-R complexes display intense absorptions in the visible region. Catalytic activity of the 1-R and 2-R complexes towards some C–C coupling reactions (e.g. Suzuki, Heck and Sonogashira) has been examined and while both are found to be efficient catalysts, 1-R is much better catalyst than 2-R.

The reaction of a 1 : 1 mixture of 4-R-benzaldehyde thiosemicarbazone [denoted in general as HL–R; where H stands for the dissociable acidic proton and R (R = OCH3, CH3, H, Cl and NO2) for the substituent] and 1-nitroso-2-naphthol (abbreviated as Hnn), with an equivalent quantity of Na2[PdCl4] in ethanolic medium affords a group of mixed-ligand complexes of the type [Pd(L–R)(nn)]. A similar reaction of a mixture of HL–R and quinolin-8-ol (Hq) with Na2[PdCl4] affords another family of mixed-ligand complexes of the type [Pd(L–R)(q)]. Crystal structures of [Pd(L–Cl)(nn)], [Pd(L–CH3)(q)] and [Pd(L–Cl)(q)] have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as monoanionic bidentate N,S-donors forming five-membered chelate rings. In the [Pd(L–R)(nn)] complexes, the 1-nitroso-2-naphtholate anion is coordinated as a N,O-donor forming a five-membered chelate ring. Similarly in the [Pd(L–R)(q)] complexes, the quinolin-8-olate anion is bound to the metal center in the N,O-mode forming a five-membered chelate ring. All the [Pd(L–R)(nn)] and [Pd(L–R)(q)] complexes show characteristic 1H NMR signals, and in dichloromethane solution they all display intense absorptions in the visible and ultraviolet regions. Catalytic activities of the [Pd(L–R)(nn)] and [Pd(L–R)(q)] complexes have been examined towards some C–C and C–N coupling reactions, where both were found to show notable catalytic efficiency.

Reaction of salicylaldehyde semicarbazone (L1), 2-hydroxyacetophenone semicarbazone (L2), and 2-hydroxynaphthaldehyde semicarbazone (L3) with [Pd(PPh3)2Cl2] in ethanol in the presence of a base (NEt3) affords a family of yellow complexes (1a, 1b and 1c, respectively). In these complexes the semicarbazone ligands are coordinated to palladium in a rather unusual tridentate ONN-mode, and a PPh3 also remains coordinated to the metal center. Crystal structures of the 1b and 1c complexes have been determined, and structure of 1a has been optimized by a DFT method. In these complexes two potential donor sites of the coordinated semicarbazone, viz. the hydrazinic nitrogen and carbonylic oxygen, remain unutilized. Further reaction of these palladium complexes (1a, 1b and 1c) with [Ru(PPh3)2(CO)2Cl2] yields a family of orange complexes (2a, 2b and 2c, respectively). In these heterodinuclear (Pd–Ru) complexes, the hydrazinic nitrogen (via dissociation of the N–H proton) and the carbonylic oxygen from the palladium-containing fragment bind to the ruthenium center by displacing a chloride and a carbonyl. Crystal structures of 2a and 2c have been determined, and the structure of 2b has been optimized by a DFT method. All the complexes show characteristic 1H NMR spectra and, intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on all the complexes shows an irreversible oxidation of the coordinated semicarbazone within 0.86–0.93 V vs. SCE, and an irreversible reduction of the same ligand within −0.96 to −1.14 V vs. SCE. Both the mononuclear (1a, 1b and 1c) and heterodinuclear (2a, 2b and 2c) complexes are found to efficiently catalyze Suzuki, Heck and Sonogashira type C–C coupling reactions utilizing a variety of aryl bromides and aryl chlorides. The Pd–Ru complexes (2a, 2b and 2c) are found to be better catalysts than the Pd complexes (1a, 1b and 1c) for Suzuki and Heck coupling reactions.

Reaction of salicylaldehyde thiosemicarbazone (L-1), 2-hydroxyacetophenone thiosemicarbazone (L-2) and 2-hydroxynapthaldehyde thiosemicarbazone (L-3) with [Ru(dmso)(4)Cl-2] affords a family of three dimeric complexes (1), (2) and (3) respectively. Crystal structure of the complex (3) has been determined. In these complexes, each monomeric unit consists of one ruthenium center and two thiosemicarbazone ligands, one of which is coordinated to ruthenium as O,N,S-donor and the other as N,S-donor forming a five-membered chelate ring. Two such monomeric units remain bridged by the sulfur atoms of the O,N,S-coordinated thiosemicarbazones. Due to this sulfur bridging, the two ruthenium centers become so close to each other, that a ruthenium-ruthenium single bond is also formed. All the complexes are diamagnetic in the solid state and in dimethylsulfoxide solution show intense absorptions in the visible and ultraviolet region. Origin of these spectral transitions has been established from DFT calculations. Cyclic voltammetry on the complexes shows two irreversible ligand oxidations on the positive side of SCE and two irreversible ligand reductions on the negative side.