The tridentate Schiff base ligand 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol (HL) was used to synthesize four new cadmium(II) complexes, namely [Cd<inf>4</inf>L<inf>6</inf>](ClO<inf>4</inf>)<inf>2</inf> (1), [CdL(SCN)]<inf>n</inf> (2), [CdL(dca)]<inf>n</inf> (3) and [CdL(N<inf>3</inf>)]<inf>n</inf> (4), with the aim of exploring the role of the coordinating and non-coordinating anion in governing the architecture as well as the photophysical behavior of the complexes. In addition to common physicochemical techniques, complexes 1 and 2 have further been characterized by X-ray single crystal structural analysis. Complex 1 is a tetranuclear cationic Cd(II) species where each metal ion has a distorted octahedral geometry. Three Cd atoms have the N<inf>4</inf>O<inf>2</inf> chromophoric environment, whereas the fourth and central Cd has an O<inf>6</inf> chromophore. Complex 2 is a polynuclear species having a 2D network of (4,4) topology where dinuclear [Cd<inf>2</inf>L<inf>3</inf>] metal entities located at the nodes are bridged by SCN- anions. The ligand and all four complexes are highly fluorescent. Quantum yield calculations reveal that the fluorescence efficiency of the complexes is higher than that of the ligand and the efficiency is largely influenced by the nature of the co-ligand. © 2015 Elsevier Ltd.

P KUNDU

E ZANGRANDO

P CHAKRABORTY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Polyhedron

Four new zinc(II) complexes of a tridentate Schiff base ligand 2-((E)-((pyridin-2- yl)methylimino)methyl)phenol (HL), namely [Zn2L2Cl2] (1); [Zn2L2Br2] (2); [ZnL(SCN)(MeOH)] (3) and [Zn2L(OAc)3(MeOH)] (4) have been synthesized with the view to investigate the role of co-ligands in controlling the structural diversity, photoluminescence property and catalytic activities. The complexes have been characterized through common physicochemical techniques as well as by X-ray single crystal structural analysis. All of them display interesting co-ligands mediated photoluminescence property the origin of which may be attributed due to ligand to metal charge transfer (LMCT) and the order of photoluminescence efficiency is 3&gt;4&gt;1~2. Catecholase and phosphatase activities of the complexes have been investigated in DMF medium using 3,5-di-tert-butylcatechol (3,5-DTBC) and 4- nitrophenylphosphate as substrates respectively. Co-ligands have prominent role on phosphatase activity of the complexes where the order of activity in terms of kcat value is 4&gt;1&gt;2&gt;3. 2 Interestingly, only complex 4 is active in catalyzing the aerobic oxidation of 3,5-DTBC. The presence of readily labile solvent molecule in one of the zinc centers of complex 4 perhaps takes the key role for initiating substrate-Zn interaction and thereby the activity. Radical pathway is the probable reason behind the catecholase activity as is evident from EPR study. Solid state thermal analysis suggests that ZnO is the thermally stable end product for complexes 1, 2 and 4, whereas it is ZnS in case of complex 3.

Influence of co-ligands in synthesis, photoluminescence behavior and catalytic activities of zinc complexes of 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol

Reaction of ZnII-acetate with two N, N, O-donor Schiff-base ligands, HL1 {4-Chloro-2-[(2-morpholin-4-yl- ethylimino)-methyl]-phenol} and HL2 {4-Chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol}, which are formed in situ via condensation of 5-chlorosalicylaldehyde and N-(2-aminoethyl/propyl)mor- pholine, produce one tri- and one mononuclear species, Zn3L1 (OAc)4 (1) and ZnL2 (OAc) (2). The hypothet- ical ZnL1 (OAc) and Zn3L2 (OAc)4 are energetically unfavorable by 9.2 and 5.1 kcal/mol, in compare with their respective real counterparts 1 and 2 evidenced from DFT calculations. Both 1 and 2 catalyze the hydrolytic cleavage of phosphoester bond of (4-nitrophenyl) phosphate where 1 shows higher activity than that of 2. The proposed mechanistic pathways of phosphatase activity of 1 and 2 and the higher effi- ciency of the latter have been rationalized by DFT study. DNA cleavage activities have been investigated using supercoiled pET28a plasmid DNA where both the complexes show dose dependent DNA cleavage activity with varying degree. Complex 1 shows excellent breakage activity even at a concentration of 20 lM. However, in both cases hydroxyl radical pathway is most probably operative in DNA cleavage activity.

Inorganica Chimica Acta

Role of ligand backbone of tridentate Schiff-base on complex nuclearity and bio-relevant catalytic activities of zinc(II) complexes: Experimental and theoretical investigations

By using two potential tridentate ligands, HL1 [4- chloro-2-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol] and HL2 [4-chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phe- nol], which differ by one methylene group in the alkyl chain, four new ZnII complexes, namely, [Zn(L2 H)2](ClO4)2 (1), [Zn(L1 )(H2O)2][Zn(L1 )(SCN)2] (2), [Zn(L1 )(dca)]n (3), and [Zn2(L1 )2(N3)2(H2O)2] (4) [where dca = dicyanamide anion] were synthesized and structurally characterized. The results indicate that the slight structural difference between the ligands, HL1 and HL2 , because of the one methylene group connecting the nitrogen atoms provokes a chemical behavior completely different from what was expected. Any attempt to isolate the Zn(L2 ) complexes with thiocyanato, dicyanamido, and azide was unsuccessful, and perchlorate complex 1 was always obtained. In contrast, with HL1 we obtained structural diversity on varying the anions, but we failed to isolate the analogous perchlorate complex of HL1 . Single-crystal X-ray analyses revealed that the morpholine nitrogen of ligand L2 is protonated and thus does not take part in coordination with ZnII in complex 1. On the other hand, the morpholine nitrogen of L1 is coordinated to ZnII in 2−4. Of these, 2 and 4 are rare examples of a cocrystallized cationic/anionic complex and of a dinuclear complex bridged by a single azide, respectively. Some of these unexpected findings and some interesting noncovalent interactions leading to the formation of dimeric entities in solid-state compound 4 were rationalized by a DFT approach. Photoluminescence properties of the complexes as well as the ligands were investigated in solution at ambient temperature and at 77 K. The very fast photoinduced electron transfer (PET) from the nitrogen lone pair to the conjugated phenolic moiety is responsible for very low quantum yield (Φ) exhibited by the ligands, whereas complexation prevents PET, thus enhancing the Φ in the complexes. The origin of the electronic and photoluminescence properties of the ligands and complexes was assessed in light of theoretical calculations.

Fulltext

Crystal Growth & Design

Combined Experimental and Theoretical Investigation of Ligand and Anion Controlled Complex Formation with Unprecedented Structural Features and Photoluminescence Properties of Zinc(II) Complexes

Reactions of zinc(II) and cadmium(II) halides with an N,N,O-donor Schiff-base ligand HL (obtained by the 1:1 condensation of salicylaldehyde and 2-(2-aminoethyl)pyridine) yield six new phenoxo bridged dinu- clear complexes of the general formula [Zn2L2X2] (1–3) and [Cd2L2X2] (4–6), where X = Cl, Br and I, respec- tively. The complexes have been characterized by routine physicochemical techniques: elemental analyses, IR, electronic spectral studies, conductivity and solid state thermal studies. Complexes 1, 2 and 6 have further been characterized by single crystal X-ray structural analyses. The ligands, as well as all six complexes, are highly fluorescent. For the ligand, the emission band is attributed to a p–p⁄ transi- tion, whereas for the complexes the emissions may be assigned to ligand-to-metal charge transfers (LMCT). Quantum yield calculations revealed that the metal complexes exhibit more intense fluorescence compared to the ligand, which is supposed to be due to the enhancement of rigidity of the ligand on che- lation, which reduces the loss of energy through non-radiative channels of the intraligand emission excited state. Thermogravimetric analyses of the complexes suggest that upon heating the thermally sta- ble final product in the case of complexes 1–3 is ZnO, 6 gives CdO, whereas for complexes 4 and 5 the final product remains unidentified.

Phenoxo bridged luminescent dinuclear zinc(II) and cadmium(II) complexes of 2-[[[2-(2-pyridyl)ethyl]imino]methyl]phenol: Crystal structure, photophysical and thermal studies

Two binuclear copper(II) complexes one (complex 1) with a macrocyclic ligand (H2L1) and other (complex 2) with a macroacyclic (end-off type) compartmental ligand (HL2) have been synthesized from single pot template synthesis involving copper(II) nitrate, 1,2- diaminoethane, 4-methyl-2,6-diformylphenol, and sodium azide. Structure analysis of complex 1 reveals that there are actually two half molecules present in the asymmetric unit and so two complexes (molecule-I and molecule-II) are present in unit cell, although they show slight differences. The two Cu(II) centers are in distorted square pyramidal coordination environment with two endogenous phenoxo bridges provided by the phenolate of H2L1 having Cu&ndash;Cu separations of 2.9133(10) A ̊ and 2.9103(10) in the two molecules. In complex 2 the coordination environments around two Cu(II) centers are asymmetric, Cu1 is in distorted square pyramidal environment whereas, the coordination environment around Cu2 is distorted octahedral. The two Cu(II) centers in complex 2 are connected by two different kinds of bridges, one is endogenous phenoxo bridge provided by the phenolate of the ligand HL2 and the other is exogenous azido bridge (l1,1 type) with Cu&ndash;Cu distance of 3.032(10) A ̊ . Variable temperature magnetic studies show that two Cu(II) centers in both the complexes are strongly antiferromagnetically coupled with J = 625 &plusmn; 5 cm1 and J = 188.6 &plusmn; 1 cm1 for complex 1 and 2, respectively.

Journal of Molecular Structure

A novel single pot synthesis of binuclear copper(II) complexes of macrocyclic and macroacyclic compartmental ligands: Structures and magnetic properties

Coordinating and non-coordinating anion controlled synthesis of different nuclearity cadmium(II) complexes of 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol: Crystal structure and photophysical study

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ISSN	0277-5387