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Nearly 80% of human chronic infections are caused due to bacterial biofilm formation. The increased resistance against the conventional antimicrobial agents makes it difficult to treat the biofilm-related infections. The antibiotics resistance developed by planktonic cells has also become a major threat for human. Therefore, we have attempted here to develop an effective alternative strategy to overcome the issues of antibiotics resistance of bacteria. Upon synthesis, biogenic C-dots were combined with lysozymes which were further encapsulated into chitosan nanocarrier to form C-dots carrier (CDC). The as-synthesized C-dots were found irregular shaped and the average size of C-dots and CDC were 8 ± 2 nm and 450 ± 50 nm, respectively. To ensure secure and targeted delivery of C-dots and lysozyme we have employed chitosan, a biodegradable and natural biopolymer, as a delivery system. The study of time-dependent bacterial growth and flow cytometry analysis demonstrated that CDC can exhibit a synergistic bactericidal activity against the antibiotics resistant recombinant E. coli cells. Further, we have shown that the CDC could be a potent agent for both prevention of biofilm formation and eradication of preformed biofilm. In addition, we have observed that our drug delivery system is hemocompatible in nature making it suitable for in vivo applications. Therefore, we believe that the combination therapy of C-dots and lysozyme may be used as an excellent antibacterial and antibiofilm strategy.

Derivatives of the types [CCul{Sn2(OR)9}] (R = Et, 1; R = Pri, 2) and [Cu{Sn2(OR)9}2] (R = Et, 3; R = Pri, 4) have been synthesised by the reactions of anhydrous CuCl2 with NaSn2(OR)9 (R = Et, Pri) in 1: 1 and 1: 2 molar ratios in benzene, respectively. The chloro(nonaalkoxodistannato)-copper(II) complexes 1–2 yield, via chloride replacement reactions with a variety of monodentate ( e.g., EtO–, PriO–) or chelating [ e.g., Al(OEt)4–, Al(OPri)4–, Zr2(OPri)9–, and Nb(OPri)6–] ligands, novel heterometallic alkoxides of copper(II). All of the complexes 1–19 are highly moisture-sensitive, coloured solids, that are soluble in typical organic solvents. They are monomeric in benzene solution and are thermally unstable under reduced pressure.

Nine heterobimetallic homoleptic diethanolaminate complexes of the types: [Nb(Rdea)3{Ta(Rdea)2}] (where Rdea = RN(CH2CH2O-)2 and R = H, 2; Me, 3; Bu n, 4; Ph, 5), [Nb(Rdea)3{Al(Rdea)}] (R = H, 6; Me, 7; Bu n, 8; Ph, 9), and [Nb(Phdea)3{Sb(Phdea)}] 10 have been prepared for the first time by the equimolar reactions of [Nb(Rdea)2(RdeaH)] with [Ta(Rdea)2(OPr i)] or [Al(Rdea)(OPr i)] or [Sb(Phdea)(OPr i)] in benzene. The structural features of the new complexes have been elucidated by IR and NMR (1H, 27Al) spectroscopies.

Reaction of VO(OPri)3 with two equivalents of N-phenyldiethanolamine (PhDEAH2) yields a homometallic complex [VO(PhDEA)(PhDEAH)] 1, which reacts with a number of metal alkoxides to afford heterobimetallic oxovanadium(V) complexes of the types [VO(PhDEA)2{M(OR)n-1}] [where PhDEA = C6H5N(CH2CH2O–)2], [M =: Al (n = 3, R = Pri) 2; Al (n = 3, R = But) 3; Ti (n = 4, R = Pri) 4; Zr (n = 4, R = Pri) 5; Nb (n = 5, R = Pri) 6; Ta (n = 5, R = Pri) 7. The derivative [VO(PhDEA)(OSiPh3)] 8 has been prepared by the equimolar interaction of [VO(PhDEA)(OPri)] with Ph3SiOH. All of these complexes have been characterised by spectroscopic (IR; 1H, 13C, 27Al and 51V NMR) studies, elemental analyses, and molecular weight measurements. The derivative 2 has also been characterised by FAB mass spectral studies, which supports for its monomeric nature.

Reactions of InCl3 with potassium salts of bifunctional tridentate (L1H2HOC6H4CH NCH2CHMeOH) and monofunctional bidentate (L2HHOC6H4CHN-i-Bu) Schiff bases in 1:1 and 1:2 molar ratio in benzene afford complexes In(L1)Cl and In(L2)2Cl, respectively. On reaction with potassium isopropoxymetallates KB(O-i-Pr)4, KAl(O-i-Pr)4, KTi(O-i-Pr)5, and KNb(O-i-Pr)6, they produce interes- ting heterobimetallic heterocyclic complexes. These are characterized by elemental (N, B, Al, Ti, and Nb) analyses, molecular weight measurements, and spectral [IR, NMR (1H, 13C, 11B, and 27Al)] studies. Probable structures are suggested for them. © 2003 Wiley Periodicals, Inc. 15:21–25, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10206

Heterotrimetallic isopropoxides of the composition [{Zr2(OPri)9}Ba{M(OPri)3}]2have been prepared by the in situ reactions of MCl2[M = Be, Mg, Zn, Sn(II], Co, Ni, Cu(II), KZr2(OPri)9and KBa(OPri)3in equimolar amounts. Reaction of [{Zr2(OPri)9}Ba{Zn(OPri)3}]2with tertiary butyl alcohol has been studied to gain an insight into its structure. All new derivatives have been characterised by elemental analyses, spectroscopic [IR, UV–VIS, and NMR (1H,13C, and119Sn)] studies and molecular weight measurements.

Hexaisopropoxoniobates/tantalates of lathanides of the type [Ln{(μ-OPr i ) 2 M(OPr i ) 4 } 3 ] (M = Nb, Ln = Y(1), La(2), Nd(3), Er(4), Lu(5); M = Ta, Ln = Y(6), Gd(7)) have been prepared by the reactions of LnCl 3 .3Pr i OH with three equivalents of KM(OPr i ) 6 in benzene. Reactions in 1:2 molar ratio of LnCl 3 .3Pr i OH with KTa(OPr i ) 6 yielded derivatives of the type [{(Pr i O) 3 Ta(μ-OPr i ) 3 }Ln{(μ-OPr i ) 2 Ta(OPr i ) 4 }(Cl)] (Ln = Y(8), Gd(9)), which on interactions with one equivalent of KOPr i afforded [{(Pr i O) 3 Ta(μ-OPr i ) 3 }Ln {(μ-OPr i } 2 Ta(OPr i ) 4 }(OPr i )] (Ln = Y(10), Gd(11)). All these derivatives have been characterized by elemental analyses and molecular weight measurements as well as by their spectroscopic [IR, 1 H and 1 3 C NMR (Y, La, Lu), electronic (Nd, Er)] studies. 8 9 Y NMR studies have also been carried out on derivatives (6), (8), and (10).

Pentaisopropoxostannate derivatives of the types [{M[Sn(OPri)5](μ–Cl)}2] and [M{Sn(OPri)5}2] have been prepared by the reactions of MCl2 (M = Mg, Zn, and Cd) with NaSn(OPri)5 in 1:1 and 1:2 molar ratios, respectively, in benzene. All these derivatives have been characterised by elemental and isopropoxo group analyses, spectroscopic (IR, 1H and 13C NMR) studies, and molecular weight determinations. Two typical hydrolytic reactions of [Zn{Sn(OPri)5}2] have also been investigated.

In view of the advantages of employing heterometallic alkoxides as precursors for ceramic materials by the sol-gel process, efforts are being made to develop novel routes for their synthesis and to design single source precursors suited to the final targeted material. Three such new pathways are briefly presented in this paper: (i) varying the ratio of constituent metals; (ii) dissolution of metal chlorides in alkoxides of tetravalent metals; and (iii) reactions of acidic protons of metal glycolate derivatives with alkoxides of another metal yielding derivatives containing other alkoxometallates in cationic form.

Reactions of BuSn(OPri)3 with two equivalents of a number of glycols (HOGOH, where G = CMe2CMe2, CH(Me)CH(Me), CMe2CH2CHMe, and CMe2CH2CH2CMe2), with varying steric bites yield metallic glycolate complexes (1), (2), (3), and (4) with one residual hydroxy group; these on reacting with Al(OPri)3 and Nb(OPri)5 in a 1:1 molar ratio yield interesting heterodimetallic compounds of the general formulae BuSn(OGO)2Al(OPri)2 and BuSn(OGO)2Nb(OPri)4. All of these derivatives have been characterised by elemental analyses, spectroscopic (IR; NMR: 1H, 27Al, and 119Sn) studies and molecular weight determinations.

Interactions of CoCl2 with K{M(OPri)6} in 1:2 molar ratio in PriOH and C6H6 result in products with the composition [Co{M(OPri)6}b42] (M=Nb or Ta) in quantitative yields. Interchange reactions of these isopropoxide derivatives with alcohols of varying steric bulk (e.g., MeOH, EtOH, PrnOH, BunOH, and ButOH, or AmtOH) yield derivatives of composition, [Co{M(OR)6}2] (R=Me, Et, Prn, and Bus); [Co{M(OPri)3(OBus)3}2]; [Co{M(OPri)5(OBut)}2] and [Co{M(OPri)2(OR)4}2] (R=But or Amt). All these novel compounds have been characterized by elemental analyses and molecular weight determinations as well as by infrared, visible spectral and magnetic studies.

A series of zirconocene(IV) halides, [Zr(η-C5H4SiMe3)2X2][X = Cl (1) or Br (2)] and [Zr{η-C5H3(SiMe3)2-1,3}2X2][X = F (3), Br (4), I (5), or Cl (6)], has been prepared, either by (i) substitutive procedures from ZrCl4[involving the following ligand exchanges: Cl–/C5H4SiMe3–, Cl–/C5H3(SiMe3)2–, Cl–/Br–, Cl–/l–, or Cl–/NMe2– followed by NMe2–/F–], or (ii), for complexes (3), (5), or (6), by oxidative addition to [Zr{η-C5H3(SiMe3)2-1,3}2(CO)2]. The only νasym(ZrX2) vibration to be assigned with confidence is for X = F at 563 cm–1; 1H and 13C n.m.r. data are unexceptional. X-Ray structure determinations of complexes (1)–(5) have been carried out. Their molecular symmetry is close to 2, or crystallographically imposed 2 in (3), with the stereochemistry about the metal centre best described as distorted tetrahedral. The angle X–Zr–X is 93.70(7), 94.2(1), 100.5(3), 100.25(5), and 100.37(4)° for the halides (1)–(5), respectively; and the corresponding centroid–Zr–centroid angles are 129.1, 128.2, 131.4, 131.4, and 131.8°. Metal–halogen distances in (1)[2.505(2) and 2.476(2)A] and (3)[2.212(6]A are significantly longer than in the parent zirconocene(IV) halides [Zr(η-C5H5)2X2](cf. 2.44 A for X = Cl and 1.98 A for X = F) as are [by ca. 0.04 A(average)] the metal–centroid distances in (3)–(5).

Oximes form monomeric complexes, MenSi(ON:CR1R2)4 –n(n= 0–3), which appear to be tetrahedral, except for the derivatives, Me3SiON:CHR (R = 2-pyridyl or 4-pyridyl) which appear to be five-co-ordinate.