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Synthesis, Crystal Structure, Low Temperature Magnetic Behavior And Biological Activity Of Schiff Base Coordinated Poly-nuclear Cu(II) Complexes
Full text linkThe main objectives of this thesis are the synthesis Schiff base coordinated polynuclear copper(II) complexes and investigate their potential application in molecular magnetism and in the area of biochemistry. Since multidentate Schiff base ligands have both bridging and chelating binding modes with metals, they often form polynuclear complexes with transition metal ions without any co-ligands. In addition to this they also form polynuclear transition metal complex in combination with various co-ligands. The polynuclear copper(II) complexes were synthesized adopting the following two methods:
i) Using multidentate Schiff base ligand containing at least two hydroxyl groups with Cu(II) salts.
ii) Using multidentate Schiff base ligand in combination with a linear dicarboxylate.
The synthesized complexes are characterized by elemental analysis, IR, NMR spectroscopy, ESI-mass, X-ray single crystal structure determination and low-temperature magnetic measurement. Variable temperature magnetic measurements were carried out and the results obtained have been correlated with their corresponding structural features. This thesis also presented the study of the interaction of polynuclear copper(II) complexes with calf-thymus DNA and serum albumins (bovine serum albumin / human serum albumin). Modes of interaction of complexes with CT-DNA and serum albumins have been explored by molecular docking studies. So, these works might be proved beneficial in the future to cater the demands of the smart materials in the various fields like material chemistry, medicinal chemistry etc. and also enrich the family of Schiff base coordinated polynuclear copper(II) complexes.
Chapter 1 contains general introduction and literature survey about 3d metal coordination compounds and their potential applications, such as magnetic, fluorescence and biological activity.
Chapter 2, describes synthesis and characterization of three novel tetranuclear copper(II) complexes namely [Cu4(L1)4]∙(dmf) (1), [Cu4(L1)4] (2) and [Cu4(L2)2(HL2)2(H2O)2]∙2(ClO4)∙6(H2O) (3) (H2L1, (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H2L2, (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol)). The complexes were synthesised by the reaction of copper(II) perchlorate and the tridentate Schiff base ligands. Complexes 1 and 2 possess face-sharing dicubane core structure, on the other hand complex 3 has double open cubane core structure. Variable temperature magnetic susceptibility measurements in the range 2-300 K indicate an overall weak antiferromagnetic exchange coupling in all complexes.
Chapter 3, present two copper(II) complexes, [Cu4(L)2(HL)2(H2O)2]∙2(ClO4)∙2(H2O)∙DMF (1) and [Cu4(L)2(HL)2(H2O)2]∙(tp) (2) [H2L = 2-ethoxy-6-[(1-hydroxymethyl-propylimino)-methyl]-phenol; tp = terephthalate] which were synthesized and characterized by single crystal X-ray diffraction and spectroscopic studies. The structural determination reveals that both the complexes are tetranuclear with double-open-cubane like core framework. Interactions of complexes with the calf thymus DNA (CT-DNA) and serum albumins were investigated using electronic absorption and fluorescence spectroscopic techniques.
Chapter 4, represent synthesis and characteization of Cu(II) complexes [Cu4(L)2(HL)2(H2O)2]∙2(pv) (1) and [Cu4(L)2(HL)2(H2O)2]∙(ssal) (2) [H2L = 2-Ethoxy-6-[(1-hydroxymethyl-propylimino)-methyl]-phenol; pv = pivalate; ssal = 2-Hydroxy-5-sulfosalicylate].
Both the complexes are tetranuclear with double open cubane core framework. C-H…π interactions results the formation of 1D supramolecular structure for both the complexes. The interactions of complexes with the calf thymus DNA, bovine serum albumin (BSA) and human serum albumin (HSA) were studied using UV-vis absorption and fluorescence spectroscopic techniques. Molecular docking technique has been used to determine the mode of interaction of complexes with CT-DNA and serum albumins.
Chapter 5, reports the synthesis of two 1D polynuclear copper(II) compounds{[Cu2(HL1)2(fum)]∙(H2O)∙(MeOH)}n(1) and {[Cu2(L2)2(tp)]∙(H2O)}n (2)(fum = fumarate ; tp = terephthalate) using alkoxo, hydroxo, phenoxo and imine donor Schiff bases [(E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol] (H2L1) and [(E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol] (H2L2). Structure determination reveals that the complexes 1 and 2 crystallize in the monoclinic system with space group P21/n and Pn, respectively. Variable temperature magnetic property study indicates overall antiferromagnetic exchange coupling in both the complexes. The interaction of complexes with calf thymus DNA (CT-DNA) and bovine / human serum albumins were studied using electronic absorption and fluorescence spectroscopic techniques.
Chapter 6, contain synthesis and characteization of two copper(II) complexes namely [Cu4(L1)4]∙0.5(H2O) (1) and [Cu4(L2)2(HL2)2(H2O)2](sq)∙2(H2O) (2) (H2L1= [(E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol], H2L2 =[(E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol], sq = squarate and tp = terephthalate ion).The structural determination reveals that complex 1 crystallizes in the triclinic system with space group Pī, whereas complexes 2 crystallize in the monoclinic system with space group P21/n. Both 1 and 2 are tetranuclear species with Cu4O4 close cubane core and double-open cubane like core structure, respectively.
Variable temperature magnetic property study indicates overall antiferromagnetic exchange coupling in both complexes. The PHI program was used to study their magnetic behavior. The Hamiltonians of type H = – J1 (S1S2 + S1S4 + S2S3 + S3S4) – J2 (S1S3+ S2S4) and H = – J1 (S1S3 + S2S4) – J2 (S1S2 + S3S4) – J3S1S4 were used to study magnetic behavior of 1 and 2, respectively, and good agreement between the experimental and simulated results were found by using the parameters: g = 2.14, J1 = -20.2 cm-1 and J2 = -1.7 cm-1 for 1, and g1 = 2.14, g2 = 2.12, J1 = -54.8 cm-1, J2 = -15.9 cm-1 and J3 = 0 cm-1 for 2
Minutes of the Departmental Committee Meeting (Economics with Rural Development) held on 04.04.2019
No full textA Cascaded Toolkit for Secure Data Transmission
Full text linkCryptography is the practice and study of techniques to hide information in storage or
transit for secure communication in the presence of adversaries. Private key cryptography
uses the same cryptographic keys for both encryptions of plaintext and decryption of
ciphertext.The keys may be identical or there may be a simple transformation to go
between the two keys. Authentication is a process that ensures a user’s identity.
Steganography is the process of hiding information using a cover carrier like text, image,
audio, and video. In the last two decades, researchers have derived new algorithms and
information hiding models using cryptography, authentication, and steganography.There
is a scope to develop a security toolkit by combining newly implemented independent
models using cryptography, authentication, and steganography all together in a cascading
manner which provides better security for transmitting data as compared to the standard
algorithms.The basic objective of the work is to design an integrated ciphering system or a so called,
‘security toolkit’. Such a system has been formed by combining a set of newly developed
independent bit-level ciphering protocols. Each of these protocols ultimately has acted as
the ‘building block’ for that implemented ‘security toolkit’. For the purpose of assessing
each ‘building block’ which has been developed during the work, different standard
algorithms and parameters have been used.The contribution of the abstract of this research is threefold. In the first part, ‘user authentication building blocks’ have been introduced based on CAPTCHA (Completely
Automated Public Turing test to tell Computers and Humans Apart) code generated from
personal information and OTP (One Time Password) formulated on biometric image.Three authentication schemes have been implemented namely “CAPTCHA Code based on User Personal information and Likings (CCUPL)”, “Secret Value based on Randomized One Time Password (SVROTP)” and “Numeric and biometric Image-based One Time Password (NIOTP)” for ‘authentication building blocks’.CAPTCHA or OTP generation time, their randomness and how they provide security over different network attacks have been considered as standard parameters for assessing the performances of newly implemented schemes.The distribution of the private key without interpretation is very hard to achieve. So, in
the second part, an attempt has been made to design a predefined secret procedure to
retrieve the secret value from the private key, as well as securing both the actual private
key value and the secret procedure from unauthorized access at the time of encrypting
character based plain text. Both the encryption and decryption have been done by the
secret value derived from the private key. Seven text encryption algorithms have been
implemented namely “Prime number with Alphabetic Group based text encryption
(PAG)”, “Palindrome number with Alphabetic Group and Operator based text encryption
(PAGO)”, “Multiple Operator and Even Odd position based text encryption (MOEO)”,
“Multiple Operator and ASCII Value based text encryption (MOAV)”, “Multiple
Operator and number of Zeros and Ones based text encryption (MOZO)”, “Armstrong
and Perfect number with Cipher Sequencing based text encryption (APCS)” and
“Amicable number with Cipher Sequencing based text encryption (ACS)” for ‘text
encryption building blocks’.Multiple parameters like time requirement for phase wise (encryption + decryption)
execution, degree of freedom value, formulation of the structure of private key being
used, Pearsonian chi-square value have been considered for measuring the performance
of ‘text encryption building blocks’. The result of each of the algorithms has been
compared with standard AES (Advanced Encryption Standard), Triple DES (Data Encryption Standard), Twofish, Blowfish and Serpent algorithms where satisfactory
outcomes have been observed.
In the third part, image partitioning, key based encryption, digital enveloping and user
defined steganographic scheme based new ‘image encryption building blocks’ have been
introduced. Three new image encryption schemes have been implemented namely “Even
Odd block based Digital Enveloping scheme (EODE)”, “Cumulative Image encryption
using Digital enveloping, Key based encryption with image Partitioning (CIDKP)” and
“Cumulative Image encryption using Steganographic scheme with Pixel repositioning
(CISP)” for ‘image encryption building blocks’.Encryption speed, cryptographic security, Mean Square Error (MSE), Peak Signal to
Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM), Universal Image
Quality Index, Bit Error Rate (BER), Correlation Coefficient (CC) and Normalized Cross
Correlation (NCC) have been considered as parameters for measuring the performances
of the implemented ‘ image encryptions building blocks’.
Based on all these and few more new parameters, the performance of each ‘building
block’ has been compared with two selected standard existing protocols. After the
successful completion of designing and developing all the ‘building blocks’ in an
independent manner, all such blocks have been cascaded by formulating proper
schematic characteristics as well as operational characteristics. A satisfactory outcome of
implementing this ‘security toolkit’ in a stand-alone system has been experienced, which
has indicated that the successful completion of this chain of actions has been ultimately
reached to the end of this research work
