New Platinum(II) and Rhenium(I) Complexes of Linear Chelate Ligands Terminated with Pyridyl or Imidazolyl N-Donor Groups

The overall goal of this dissertation research is to design, synthesize, and study new Pt(II) and Re(I) complexes relevant to biomedical applications. One of the projects involves the assessment of the interactions of bulky tridentate carrier ligands with a bound guanine nucleobase derivative (G) in platinum complexes, with a goal of developing chemistry potentially relevant to active anti-cancer Pt drugs. In another project, the fac-[ReI(CO)3]+ core is used to prepare novel Re(I) complexes with the purpose of developing new linking chemistry relevant to 99mTc and 187Re radiopharmaceuticals. This research explores the use of three different types of linear carrier-ligands in approaches directed toward achieving the stated goals. The first type of linear tridentate carrier ligand employed (N(R)1,1′-Me2dma, when R = H, bis(1-methyl-2-methylimidazolyl)amine) is terminated by imidazolyl rings and has a central N-donor with an NH or an N−C bond. High in-plane steric bulk in monofunctional Pt(II) complexes is a feature associated with increased anti-cancer activity. Therefore, understanding carrier-ligand steric effects is crucial in designing new platinum drugs. For that purpose, the new N(R)1,1′-Me2dma ligands were utilized to synthesize [Pt(II)(N(R)1,1′-Me2dma)Cl]Cl complexes. The chemical behavior of adducts of simple purine derivatives (G) made with these monofunctional Pt(II) complexes was studied. The ligands and complexes were characterized using NMR spectroscopy, single-crystal X-ray crystallography and ESI mass spectrometry. Solution NMR spectroscopy was used as the primary tool to study the Pt(II)(N(R)1,1′-Me2dma)G adducts. During this work, the 3′-GMP mono adduct of [Pt(N(H)1,1′-Me2dma)Cl]Cl complex was crystallized, allowing the first crystallographic molecular structure determination for a 3′-GMP platinum(II) complex. The other two types of linear tridentate ligands have the central N donor in a sulfonamide linkage. New ligands terminated with either two pyridyl rings (second type, N(SO2R)3,3′,5,5′-Me4dpa and N(SO2R)6,6′-Me2dpa, derivatives of 2-dipicolylamine) or with two imidazolyl rings (third type, N(SO2R)1,1′-Me2dma) were prepared. Pt(II) and Re(I) complexes of these new ligands were synthesized and their chemical properties studied

Looking for new horizons in water treatment at Thuruwila Lake

Even though, the developed countries have put a great attention on the formation of disinfection by-products in chlorinated water, the developing countries still have to play a significant role on this. Consequently, the consumers are at a hidden threat, which has to be exposed. This paper talks about the possibility for formation of by-products in water treatment systems in Sri Lanka, giving special attention on formation of Trihelomethane. The Thuruwila Water Treatment Plant has been designed to provide water for the Anuradhapura Township and its suburbs. Even though the plant is equipped with advance water treatment technology, it faces many complex issues which are common for all the treatment plants, extract raw water from lakes or tanks at tropical conditions. However, there are many possible ways of contamination due to many anthropogenic activities such as excessive use of agro-chemicals, improper settlements, etc. The chemicals, consist of nitrogen and phosphorous, provide appropriate conditions to toxic algae for blooming at dry zone temperatures. This results very complex situation in water bodies, leading unknown health effects at the end. The writers of this paper expect to review the capability of advance water treatment technologies in surface water treatment and make critical evaluation on the available water treatment options to open new directions, regard to more convenient and acceptable water related infrastructure development in dry zone of the country

Backup support for sustainable RWS in Sri Lanka

In Sri Lanka, during the last few decades, many sector projects launched under international donor assistance have provided drinking water facilities in rural areas. Projects implemented at the beginning have concentrated on providing the facilities, with less emphasis on sustainability and no clear policy about the management responsibility. This saw the facilities provided becoming dilapidated or abandoned, making them ineffective in achieving ultimate objectives. It was also evident that when the communities served are dispersed, remote and relatively small, management by a central body is difficult. Hence, emphasis has lately been given to sustainability aspects, such as adopting demand driven approaches, making beneficiary communities responsible for management of facilities and recognising and empowering Community Based Organisations (CBOs)

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl\u3csub\u3e2\u3c/sub\u3e Complexes with Rare Eight-Membered Chelate Rings

Copyright © 2018 American Chemical Society. NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Mendpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6′-positions (n = 2) or 3,3′,5,5′-positions (n = 4) of the pyridyl rings. The N(SO2R)3,3′,5,5′-Me4dpa ligands are coordinated in a bidentate fashion in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO2R)6,6′-Me2dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [trans-Pt(DMSO)Cl2]2(N(SO2R)6,6′-Me2dpa). The monodentate instead of bidentate N(SO2R)6,6′-Me2dpa coordination is attributed to 6,6′-Me steric bulk. These binuclear complexes are indefinitely stable in DMF-d7, but in DMSO-d6 the N(SO2R)6,6′-Me2dpa ligands dissociate completely. In DMSO-d6, the bidentate ligands in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes also dissociate, but incompletely; these complexes provide rare examples of association-dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes undergo monosolvolysis in DMSO-d6 to form the [Pt(N(SO2R)3,3′,5,5′-Me4dpa)(DMSO-d6)Cl]+ cations. However, unlike typical cis-PtLCl2 complexes, the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes are well positioned to form strong Pt-N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt(N(SO2R)3,3′,5,5′-Me4dpa)Cl2 complexes arise from steric consequences imposed by the -CH2-N(SO2R)-CH2- chain in the eight-membered chelate ring

A Very Rare Example of a Structurally Characterized 3′-GMP Metal Complex. NMR and Synthetic Assessment of Adducts Formed by Guanine Derivatives with [Pt(L\u3csup\u3etri\u3c/sup\u3e)Cl]Cl Complexes with an N,N′,N″ Tridentate Ligand (L\u3csup\u3etri\u3c/sup\u3e) Terminated by Imidazole Rings

© 2017 American Chemical Society. [Pt(N(R)-1,1′-Me2dma)Cl]Cl complexes with tridentate ligands (bis(1-methyl-2-methylimidazolyl)amine, R = H; N-(methyl)bis(1-methyl-2-methylimidazolyl)amine, R = Me) were prepared in order to investigate Pt(N(R)-1,1′-Me2dma)G adducts (G = monodentate N9-substituted guanine or hypoxanthine derivative). Solution NMR spectroscopy is the primary tool for studying metal complexes of nucleosides and nucleotides because such adducts rarely crystallize. However, [Pt(N(H)-1,1′-Me2dma)(3′-GMPH)]NO3·5H2O (5) was crystallized, allowing, to our knowledge, the first crystallographic molecular structure determination for a 3′-GMP platinum complex. The structure is one of only a very few structures of a 3′-GMP complex with any metal. Complex 5 has the syn rotamer conformation, with 3′-GMP bound by N7. All Pt(N(R)-1,1′-Me2dma)G adducts exhibit two new downfield-shifted G H8 signals, consistent with G bound to platinum by N7 and a syn/anti rotamer mixture. Anticancer-active monofunctional platinum(II) complexes have bulky carrier ligands that cause DNA adducts to be distorted. Hence, understanding carrier-ligand steric effects is key in designing new platinum drugs. Ligand bulk can be correlated with the degree of impeded rotation of the G nucleobase about the Pt-N7 bond, as assessed by the observation of rotamers. The signals of syn and anti rotamers are connected by EXSY cross-peaks in 2D ROESY spectra of Pt(N(H)-1,1′-Me2dma)G adducts but not in spectra of Pt(N(H)dpa)G adducts (N(H)dpa = bis(2-picolyl)amine), indicating that rotamer interchange is more facile and carrier-ligand bulk is lower in Pt(N(H)-1,1′-Me2dma)G than in Pt(N(H)dpa)G adducts. The lower steric hindrance is a direct consequence of the greater distance of the G nucleobase from the H4/4′ protons in the N(R)-1,1′-Me2dma carrier ligand in comparison to that from the H6/6′ protons in the N(H)dpa carrier ligand. Although in 5 the nucleotide is 3′-GMP (not the usual 5′-GMP) and the N(H)-1,1′-Me2dma carrier ligand is very different from those typically present in structurally characterized Pt(II) G complexes, the rocking and canting angles in 5 adhere to long-recognized trends

Low cost GIS data base solution for water utility network in Sri Lanka

In 1999 National Water Supply and Drainage Board (NWSDB) commenced developing a Water Utility GIS for the Greater Colombo(GC) area with the objective of improving its operations and maintenance activities. National Survey Department of Sri Lanka was contracted out to produce 1:1000 scale 3D digital base maps from Air Photographs. Available water utility maps were digitized using Autocad Map GIS and updated using Global Positioning Systems and other survey methods. Due to voluminous nature of base maps and utility data it is impractical to store them as a one seamless coverage. Storing these data as separate map tiles leads to several practical constraints such as updating difficulties, searching delays and data retrieval problems. Therefore it is required to develop a Geo-database to efficiently manage these data. It is not feasible to utilize available commercial Geo-databases for this purpose due to their high purchasing and maintenance costs. As a solution PostgreSql, a free Open Source Object Relational Database Management System(ORDBMS) was selected. PostgreSql has a module called PostGIS which handles spatial data and is used by hundreds of similar organization around the world. The software successfully runs on Linux Operating System, which also is a freeware. Geo-database was established in PostgreSQL ORDBMS with necessary table structures, relations etc., to store and manage geometric/attribute data of water features including 3D basemap data. A user friendly interface was developed within Autocad Map GIS to handle data uploading and retrievals. All necessary procedures were introduced to the organization for the efficient management of the Geo-database. Further, an Intranet Web Map Browser was developed to browse the data. Currently the system has 18 themes with total objects of around 800,000 and successfully used by all Water Manager Regions in GC area for their day-to-day activities. This implemented solution provides an excellent platform for the NWSDB to do advance geo data management for low cost

User management for sustainable rural water resources

User management for sustainable rural water resource

Community training for successful management in rural water supply

Community training for successful management in rural water suppl

Capacity building for sustainable RWS in Sri Lanka

Capacity building for sustainable RWS in Sri Lank