International conference on Frontiers in Chemical Technology 2020 (FCT 2020)
http://repository.kln.ac.lk/handle/123456789/21614
2024-03-29T15:01:41ZSynthesis of DPA based NNN donor ligands having piperidinyl groups and their platinum complexes towards potent anti-cancer applications
http://repository.kln.ac.lk/handle/123456789/21679
Synthesis of DPA based NNN donor ligands having piperidinyl groups and their platinum complexes towards potent anti-cancer applications
Peiris, P. A. L.; Perera, N. T.
Dipicolylamine (dpa) moiety has received much attention due to its coordination versatility. Our
objective is to incorporate piperidinyl groups into the dpa system due to possibility of the piperidinyl
group to target sigma receptors as it shows high affinity to sigma receptors, which are expressed in
high densities in breast cancer cells. In this study, two novel ligands; N((CH2)2piperidine)dpa (L1)
and N((CH2)3piperidine)dpa (L2) (Figure 1) were synthesized by utilizing pendant piperidinyl groups
having different chain lengths. The platinum complexes of novel ligands; [PtClN((CH2)2piperidine)
dpa]Cl (C1) and [PtClN((CH2)3piperidine)dpa]Cl (C2) were also synthesized during the study.
Structural data obtained from single crystal X ray diffraction for C1 confirms that L1 serves
as a tridentate donor ligand. UV visible spectra of both ligands and complexes were recorded in
methanol. Absorption peaks in 200-300 nm range in UV visible spectra of ligands are due to intra
ligand π→π* transitions and peaks above 300 nm range are due to n→π* transitions in the ligands.
As expected, no absorption peaks corresponding to n→π* transitions were observed in UV visible
spectra of complexes due to lack of lone pairs in the coordination complexes. Methylene protons
observed as a singlet (3.87 ppm) in 1H NMR spectrum of L1. The N-H bond of secondary amine
group present in dpa gives an IR band in 3310-3350 cm-1 region. However, IR spectra of both ligands
and complexes gave no transmittance peaks in region 3310-3350 cm-1 confirming the absence of the
N-H group which also confirms the formation of ligands and complexes. Both ligands displayed
intense fluorescence in methanol. However, fluorescence spectra of platinum complexes showed
lower intensities than the respective ligands, possibly indicating static quenching of fluorescence
upon coordination to metal. These ligands and complexes can be explored towards treatment of
breast cancer due to incorporation of piperidinyl group.
2020-01-01T00:00:00ZSynthesis of platinum complexes with N^N- sulphonamide ligands towards fluorescence imaging applications
http://repository.kln.ac.lk/handle/123456789/21678
Synthesis of platinum complexes with N^N- sulphonamide ligands towards fluorescence imaging applications
Hettige, I. L.; Perera, N.T.
Ethylenediamine has been used as the backbone to synthesize the novel Pt-N^N complexes. The
outstanding binding ability of ethylenediamine allows it to be used in the synthesis of hydrophilic
ligand systems, by substituting the terminal amine group with bulky aromatic sulphonamide
fragments which would also incorporate lipophilicity as well as enhanced fluorescence. Employing
such amphipathic ligand systems would be an optimal approach of synthesizing platinum coordination
complexes for biological applications with improved uptake by targeted cells. In this study, two
ligands (L1=N(SO2biphenyl)ethylenediamine, L2=N(SO2azobenzene)ethylenediamine) (Figure 1)
and their corresponding novel platinum complexes(C1=PtCl2(N(SO2biphenyl)ethylenediamine),
C2=PtCl2(N(SO2azobenzene)ethylenediamine)) were synthesized. UV-Visible spectra of the ligands
indicate clear changes from starting material along with the presence of intra-ligand π→π* and n→π*
transitions, giving rise to absorption peaks around 200-400 nm. Shifts of these peaks can be observed
in the UV-Visible spectra of the complexes related to MLCT transitions. The strong S-N band
detected in the FTIR spectra of the ligands is found at 820 cm-1 in L1 and 842 cm-1 in L2 and shifts
to lower wavenumbers in ethylenediamine complexes (801 in C1 and 836 cm-1 in C2) due to direct
donation of nitrogen lone pair to platinum. Disappearance of the -NH and -NH2 stretching vibration
frequency in the FTIR spectra of the complexes, found around 3300 cm-1 in the ligands, indicates the
deprotonation of the amine groups on coordination in the complex. Methylene protons of the amine
moiety of the ligands can be seen to be magnetically inequivalent in L1 and L2, appearing as triplets
within the 2.00 - 3.00 ppm range in 1H NMR spectra. Complexes display slightly higher fluorescence
intensity compared to the ligands, possibly due to rigidification of the ligand systems on developing
the coordination complex. Structural data was obtained from single crystal X-ray diffraction of L2
and C1 which validated the formation of the ligand and complex.
2020-01-01T00:00:00ZNovel fluorescence sensors for determination of Fe3+ in biological systems using sulfonamide derivatives of dipicolylamine ligands
http://repository.kln.ac.lk/handle/123456789/21677
Novel fluorescence sensors for determination of Fe3+ in biological systems using sulfonamide derivatives of dipicolylamine ligands
Vitharana, K. V. N. N.; Perera, N. T.; Cooray, A.; Deraniyagala, S. P.
Since fluorescence techniques are highly demanded area in biological species detection, the main
objective of this research was to develop real-time, ratiometric fluorescence sensors which can
be used for iron cation detection in physiological systems with high sensitivity and selectivity.
Previously synthesized and characterized two new ligand systems were developed into ratiometric
fluorescence probes for biological Fe3+ ion detection. Both ligands were sulfonamide derivatives
of dipicolylamine with two different R groups, biphenyl (L1=N(SO2biphenyldpa) and azobenzene
(L2=N(SO2azobenzdpa). The ligands were soluble at 0.2%(v/v) methanol solutions. Both L1 and L2
displayed ratiometric change with Fe3+ ions at 319 and 458 nm respectively. L2 had a relatively high
photostability, fluorescence increasing mechanism and a lower detection limit of 18.22 nM which is a
suitable concentration for biological iron detection with high sensitivity and high selectivity. L1 had
a lower detection limit of 0.674 μM and fluorescence increasing and decreasing mechanisms. Since
both ligands had minimum interferences from other common metal cations such as K+, Na+, Ca2+,
Mg2+, Ba2+, Fe2+, Cu2+ and Zn2+, the selectivity was considered to be very high. The pH sensitivity of
the both ligands were also considerably low. L2-Fe3+ complex was blue green in color with a possible
applicability for common fluorescence microscopes. Both ligands metal complexes had higher
UV-Visible absorbance than their respective free ligands. The ligands could be recovered from the
metal complexes with the addition of ethylenediaminetetraacetic acid (EDTA). All the experimental
procedures were carried out at physiological pH, 7.4 using HEPES buffer system. Beside the
biological systems the probes are applicable for other environmental and industrial samples to ferric
iron detection.
2020-01-01T00:00:00ZDetermination of total phenolic content (TPC) of Nymphaea nouchali and Nymphaea pubescens by Folin Ciocalteu method
http://repository.kln.ac.lk/handle/123456789/21676
Determination of total phenolic content (TPC) of Nymphaea nouchali and Nymphaea pubescens by Folin Ciocalteu method
Sundaram, T. M.; Napagoda, M. T.; Wijesekera, K. D.; Wijayaratne, Gaya Bandara
Nymphaea nouchali (Nil Manel) and Nymphaea pubescens (Olu) are aquatic plants, and have a long
history of use as food and folk medicine in many countries. Many phenolic compounds isolated from
these two plant species have exhibited antioxidants properties and some simple phenolic compounds
have shown to possess various pharmacological activities, including anti-inflammatory, antiproliferative,
antioxidant and pro-apoptotic potential. The aim of the present study was to determine
the content of total phenol in an extract from N. nouchali and N. pubescens flowers collected from
Galle, Sri Lanka, by a UV/Vis spectrophotometric method. Aqueous methanol (80%) was used as the
solvent to extract flowers including petals, stamens and pistil and all extracts were analyzed for TPC
by Folin Ciocalteu method. Results were expressed in terms of gallic acid equivalence in (GAE)/g dry
weight (DW) of flower part. N. pubescens petals contained 49.780 ± 0.626, stamens 37.581 ± 0.477
and pistil 31.889 ± 0.711, while N. nouchali petals showed 22.536 ± 0.383, stamens 38.702 ± 1.112 and
pistil 30.119 ±1.116 GAEg-1. N. pubescens showed higher TPC in every plant part tested compared to
N. nouchali and petal extract of N. pubescens showed highest TPC. Hence, N. pubescens flowers are a
good source of antioxidants. Results emphasized that N. nouchali and N. pubescens extracts have high
phenolic content and the importance of the use of natural products to treat pathological conditions.
2020-01-01T00:00:00Z