Synthesis, characterization, EDX, thermal, antioxidant, antibacterial, topographical, and gas adsorption studies of supramolecular tetraammoniumplatinate

Article abstract of DOI:10.1080/00958972.2013.763230

Reaction of K₂PtC₁₄ with N-alkyl-N-benzyl-N,N- dimethyl ammonium chloride (n = 8, 10, 12 and 14 for alkyl) yielded supramolecular bis(benzyldimethylalkylazaniumyl) tetrachloroplatinumdiuide (metallobenzalkonium8 (MBK8), MBK10, MBK12,

Full text of DOI:10.1080/00958972.2013.763230

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Synthesis, characterization,
EDX, thermal, antioxidant,
antibacterial, topographical, and gas
adsorption studies of supramolecular
tetraammoniumplatinate
R.K. Ameta a , Man Singh a & R.K. Kale a
a School of Chemical Sciences, Central University of Gujarat ,
Gandhinagar , India
Accepted author version posted online: 17 Jan 2013.Published
online: 21 Feb 2013.
To cite this article: R.K. Ameta , Man Singh & R.K. Kale (2013) Synthesis, characterization,
EDX, thermal, antioxidant, antibacterial, topographical, and gas adsorption studies of
supramolecular tetraammoniumplatinate, Journal of Coordination Chemistry, 66:4, 551-567, DOI:
10.1080/00958972.2013.763230
To link to this article: http://dx.doi.org/10.1080/00958972.2013.763230
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Journal of Coordination Chemistry
Vol. 66, No. 4, 20 February 2013, 551–567
Synthesis, characterization, EDX, thermal, antioxidant,
antibacterial, topographical, and gas adsorption studies of
supramolecular tetraammoniumplatinate
R.K. AMETA, MAN SINGH* and R.K. KALE
School of Chemical Sciences, Central University of Gujarat, Gandhinagar, India
(Received 14 August 2012; in final form 11 October 2012)
Reaction of K2PtCl4 with N-alkyl-N-benzyl-N,N-dimethyl ammonium chloride (n = 8, 10, 12 and
14 for alkyl) yielded supramolecular bis(benzyldimethylalkylazaniumyl) tetrachloroplatinumdiuide
(metallobenzalkonium8 (MBK8), MBK10, MBK12, MBK14) characterized with spectroscopic and
energy dispersive X-ray techniques. X-ray difraction powder analysis was performed which con-
firmed the crystalline nature of the compound. UV/Vis study performed in dimethylformamide,
dimethylsulphoxide (DMSO)/H2O, and DMSO/phosphate buffers under physiological conditions
show stability of the supramolecular units, ½ðC6H5CH2NðCH3Þ ðCnH2nþ1Þꢀþ with [PtCl4]2ꢁ. Zeta
potential with particle size distribution of MBK8 obtained with DLS-confi2rmed agglomeration of
2
the coordinate units. Thermal analysis by differential scattering calorimetric showed an effect of
alkyl chain on their heat retention. For MBK8, topographical analysis and specific surface area
were investigated with atomic force microscopy and nitrogen adsorption method, illustrating an
outstanding alignment in arrays of ionic units, and an extent of apparent cross-sectional areas,
respectively. Antioxidant and antibacterial activities were determined with 1–2,5-diphenyl-2-pic-
rylhydrazyl-scavenging effect and Gram-positive and Gram-negative bacteria, respectively. The
compounds exhibited activities for both scavenging and bacteria.
Keywords: MBK; Adsorption; Antioxidant; Biological activity
1. Introduction
Platinum-based halide salts (Magnus green and derivatives) have been of interest in
material sciences, solid state, and catalyst chemistry with significant historical importance
[1–16]. These are potent occupational sensitizing agents capable of inducing hypersensitiv-
ity in refineries [17]. Many platinum salts have been studied for their effects on the
production of IgE antibody to unrelated antigens, such as ovalbumin in adjuvant primed
animals [18]. Magnus green salt is a quasi-1-D [Pt(NH3)4][PtCl4] compound comprising
linear arrays of platinum(II) both cationic and anionic. Recently, soluble and processable
derivatives of Magnus salt have been synthesized by substituting ammonia with linear and
branched amino alkanes [19]. In this article, we replaced the cationic part by a quaternary
ammonium group where electrostatic communications between oppositely charged
coordination units led to stacking of the coordination units of salt into a quasi-1-D struc-
ture, rather than bond formation as in Magnus salt [1,20,21–37].
*Corresponding author. Email: mansingh@cug.ac.in
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online Ó 2013 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2013.763230

552
R.K. Ameta et al.
Salts of quaternary ammonium bases (QAB) are traditionally considered as effective
extracting agents for metals of the platinum group [38], used for metal extraction through
an anion exchange mechanism [39–42]. The chosen QAB (Benzalkonium Chloride, BKC)
as cationic part of ½ðC6H5CH2NðCH3Þ ðCnH2nþ1Þꢀþ [PtCl4]2ꢁ units are broad-spectrum
2
2
antimicrobial agents [43]. BKC is frequently used as a preservative in several available oph-
thalmic aqueous/non-aqueous solutions, nebulizer compounds, and nasal sprays. It is a cat-
ionic detergent whose surface-active configuration is accountable for its rapid and
prolonged incorporation into cell lipid membranes [44]. The same features of BKC make it
useful as disinfectants, biocides, and detergents, but also as antielectrostatics of phase trans-
fer catalysts [45]. BKC is bactericidal and antimicrobial with changes of n-alkyl chain
length enhancing antimicrobial activity; for example, the C12-homolog is most effective
against yeast and fungi, the C14-homolog against Gram-positive bacteria and C16-homolog
against Gram-negative bacteria [46]. BKC is widely accepted as preservatives for ophthal-
mic, parenteral products, and disinfectants for medical equipment [47–50]. It may be con-
sidered for efficacy trials in the reduction of mother to child transmission of HIV, possibly
in combination with other compounds, such as short course antiretroviral prophylaxis whose
efficacy has been demonstrated [51].
Synthesis of supramolecular compounds of tetrachloroplatinate with BKC could lead to
further advances in medical sciences, pharmaceutical, nanotechnology, industrial progres-
sions, and others. Square-planar PtX4 assemblies (X = Cl, Br) are classical Werner-type
transition metal complexes [52,53]. They are involved in a number of catalytic reactions
and have been extensively studied [54–69]. Developing metallic supramolecular
compounds with properties of platinum (anticancer) and BKC (potential antimicrobial,
antiviral, antifungal activities) may advance medicinal and industrial fields [70]. Despite
the possibilities of QAB incorporating tetrachloroplatinate, there are no reports on ionic
supramolecular frameworks of tetrachloroplatinate with the BKC. Thus, studies on bis(ben-
zyldimethylalkylazaniumyl) tetrachloroplatinumdiuide comprising [n-C8H17-n-C6H5CH2,-n,
n-(CH3)2N]2[PtCl4], [n-C10H21-n-C6H5CH2-n,n-(CH3)2N]2[PtCl4], [n-C12H25-n-C6H5CH2-n,
n-(CH3)2N]2[PtCl4], and [n-C14H29-n-C6H5CH2-n,n-(CH3)2N]2[PtCl4] having hydrophobic
and hydrophilic domains may develop useful molecules.
2. Experimental
2.1. Materials and methods
Potassium tetrachloroplatinate (K2PtCl4, 99.99%) and BKCs (>99.5%) were procured from
Sigma Aldrich. Milli-Q water was used as solvent. The complexes were identified by FT-
IR (Perkin Elmer) in KBr plates with polystyrene thin film as calibration standard. Powder
X-ray difraction (XRD) patterns were taken by XRD, PTS 3000 by Rich-Seifert. Elemental
1
analyzes were performed with the Euro vector instrument. H NMR spectra were recorded
in CDCl3 (NMR grade, 99.99%) with a Bruker-Biospin Avance-III 500 MHz FT-NMR.
For chemical shifts, TMS was used as the internal standard. Mass spectra were measured
on an Agilent Q-TOP LC/MS with both modes. In ESI+ mode, acetonitrile and water were
in 3:7 ratios as mobile phase, and in ESIꢁve mode, aqueous ammonium acetate (100 mM)
and acetonitrile were used in 1 : 11 ratio. Qualitative analyzes for Pt, Cl, N, and C were
conducted with SEM–Energy Dispersive X-ray (EDX).

Tetraammoniumplatinate
2.2. General consideration for synthesis
553
Synthesis of metallobenzalkoniums (MBKs) using K2PtCl4 and BKC in 1 : 2 ratio was per-
formed in nitrogen. The aqueous solutions were separately prepared for K2PtCl4 in 15 ml of
water and BKC in 15 mL water. The BKC solution was added to the K2PtCl4 solution drop-
wise with stirring (500 rpm). On addition of the BKC solution, the platinum salt precipitated,
but on increasing the stirring to 1200 rpm, the precipitate disappeared. The mixture after
16 h produced a light pink precipitate which was filtered off and washed with water and eth-
anol several times separately and dried in a vacuum oven overnight. The compounds were
powders and insoluble in water and ethanol, slightly soluble in acetonitrile and completely
soluble in chloroform, dimethylformamide (DMF) and dimethylsulphoxide (DMSO).
2.2.1. Bis(benzyldimethyloctylazaniumyl)tetrachloroplatinumdiuide. Two
hundred
milligrams of K2PtCl4 (0.48 mmol) and 284.9 mg (0.96 mmol) octylbenzalkoniumchloride
were taken separately. Anal. calcd for C34H60N2Cl4Pt (%): C, 48.98; H, 7.25; N, 3.36.
Found: C, 48.88; H, 7.12; N, 3.30. Spectral data: FTIR (KBr): ν (–CH3) 3034.7, 3014,
2989.8 cmꢁ1, ν(–CH2) 2953, 2928, 2855.1 cmꢁ1, ν(Ar–CH) 883.67 cmꢁ1, ν(mono substi-
tute Ar) 785.71, 720.4, 704.08 cmꢁ1, ν(C–N) 1218.4, 1165.3 cmꢁ1, ν(Pt – N) 520.4,
451.02 cmꢁ1 1H NMR (CDCl3): δ 0.890–0.864 (t, J = 13.00 MHz, 3H, CH2CH2CH3),
.
1.334–1.246 (m, 8H, (CH2)4), 1.459–1.417 (m, 2H, CH2CH2CH3), 1.868 (m, 2H,
CH2CH2N+), 3.598 (s, 6H, (CH3)2N+), 3.85–3.822 (t, J = 16 MHz, 2H, CH2N+); 5.217 (s,
2H, PhCH2N+), 7.436 (s, 3H, Ph), 7.842–7.832 (d, J = 4.5 MHz, 2H, Ph). The +ve
ESI-MS: m/z 248.2390 [M+] (calc. for [C17H30N]+ = 248.44), ꢁve ESI-MS: m/z 389.6122
[M-1 + NH4Cl] (calc. for [PtCl4 + NH4Cl] = 390.381). UV/Vis in DMF: λmax [ɛ
(dm3molꢁ1cmꢁ1)] = 260 (1443), 335 (179.5), 400 (135.5) nm, in DMSO: water (1 : 1):
λmax [ɛ (dm3molꢁ1cmꢁ1)] = 270 (1611), 335 (263) nm, in DMSO: phosphate buffer (1 : 1):
λmax [ɛ (dm3molꢁ1cmꢁ1)] = 255 (1146), 305 (184.5) nm.
2.2.2. Bis(benzyldimethyldecylazaniumyl)tetrachloroplatinumdiuide. Two
hundred
milligrams of K2PtCl4 (0.48 mmol) and 299.4 mg (0.96 mmol) decylbenzalkoniumchloride
were taken separately. Anal. calcd for C38H68N2Cl4Pt (%): C, 51.29; H, 7.70; N, 3.15.
Found: C, 51.21; H, 7.62; N, 3.10. Spectral data: FTIR (KBr): ν(–CH3) 3071.4, 3018.4,
2977.6 cmꢁ1, ν(–CH2) 2953, 2924.5, 2855.1 cmꢁ1, ν(Ar–CH) 871.43 cmꢁ1, ν(mono substi-
tute Ar) 777.55, 732.65, 704.08 cmꢁ1, ν(C–N) 1218.4, ν(Pt – N) 557.14, 479.6,
451.02 cmꢁ1 1H NMR (CDCl3): δ 0.907–0.880 (t, J = 13.5 MHz, 3H, CH2CH2CH3),
.
1.335–1.247 (m, 12H, (CH2)6), 1.473–1.415 (m, 2H, CH2CH2CH3), 1.867 (m, 2H,
CH2CH2N+), 3.597 (s, 6H, (CH3)2N+), 3.842–3.809 (t, J = 16.5 MHz, 2H, CH2N+), 5.212
(s, 2H, PhCH2N+), 7.439 (s, 3H, Ph),7.836–7.827 (d, J = 4.5 MHz, 2H, Ph). ESI-MS: m/z
276.2703 [M+] (calc. for [C19H34N]+ = 276.50). –ve ESI-MS: m/z 389.6122 [M-1
+ NH4Cl] (calc. for [PtCl4 + NH4Cl]
=
390.381). UV/Vis in DMF: λmax [ɛ
(dm3molꢁ1cmꢁ1)] = 260 (1398), 335 (12.5), 400 (82.5) nm, in DMSO: water (1 : 1): λmax
[ɛ (dm3molꢁ1cmꢁ1)] = 260 (1159.5), 355 (193) nm, in DMSO: phosphate buffer (1 : 1):
λmax [ɛ (dm3molꢁ1cmꢁ1)] = 255 (1159.5), 305 (193) nm.
2.2.3. Bis(benzyldimethyldodecylazaniumyl)tetrachloroplatinumdiuide. Two hundred
milligrams of K2PtCl4 (0.48 mmol) and 327.4 mg (0.96 mmol) dodecylbenzalkoniumchloride

554
R.K. Ameta et al.
were taken separately. Anal. Calcd for C42H76N2Cl4Pt (%): C, 53.33; H, 8.10; N, 2.96.
Found: C, 53.26; H, 8.01; N, 2.89. Spectral data: FTIR (KBr): ν(–CH3) 3067.3,
3022.4 cmꢁ1, ν(–CH2) 2916.3, 2851 cmꢁ1, ν(ArꢁCH) 875.51 cmꢁ1, ν(mono substitute Ar)
1
781.63, 732.65, 704.08 cmꢁ1, ν(C–N) 1218.4, ν(Pt – N) 557.14, 479.6 cmꢁ1. H NMR
(CDCl3): δ 0.914–0.887 (t, J = 13.5 MHz, 3H, CH2CH2CH3), 1.329–1.244 (m, 16H, (CH2)8),
1.453–1.425 (m, 2H, CH2CH2CH3), 1.863 (m, 2H, CH2CH2N+), 3.598 (s, 6H, (CH3)2N+),
3.843–3.81 (t, J = 16.5 MHz, 2H, CH2N+), 5.218 (s, 2H, PhCH2N+), 7.435 (s, 3H, Ph),
7.841–7.832 (d, J = 4.5 MHz, 2H, Ph). ESI-MS: m/z 304.3025 [M+] (calc. for [C21H38N]+
= 304.55). –ve ESI-MS: m/z 389.6122 [M-1 + NH4Cl] (calc. for [PtCl4 + NH4Cl]=390.381).
UV/Vis in DMF: λmax [ɛ (dm3molꢁ1cmꢁ1)] = 260 (1080.5), 335 (52.5), 400 (42.5) nm, in
DMSO: water (1 : 1): λmax [ɛ (dm3molꢁ1cmꢁ1)] = 270 (1699), 335 (261.5) nm, in DMSO:
phosphate buffer (1 : 1): λmax [ɛ (dm3molꢁ1cmꢁ1)] = 260 (1310), 305 (254.5) nm.
2.2.4. Bis(benzyldimethyltetradecylazaniumyl)tetrachloroplatinumdiuide. Two hun-
dred milligrams of K2PtCl4 (0.48 mmol) and 389.3 mg (0.96 mmol) tetradecylbenzalkonium-
chloride were used. Anal. Calcd for C46H84N2Cl4Pt (%): C, 55.14; H, 8.45; N, 2.80. Found:
C, 55.06; H, 8.33; N, 2.71. Spectral data: FTIR (KBr): ν(–CH3) 3034.7 cmꢁ1, ν(–CH2)
2920.4, 2855.1 cmꢁ1, ν(Ar–CH) 895.92 cmꢁ1, ν(mono substitute Ar) 789.8, 724.49,
1
704.08 cmꢁ1, ν(C–N) 1218.4, ν(Pt – N) 524.49, 451.02 cmꢁ1. H NMR (CDCl3): δ 0.913–
0.886 (t, J = 163.5 MHz, 3H, CH2CH2CH3), 1.316–1.270 (m, 20H, (CH2)10), 1.411–1.382
(m, 2H, CH2CH2CH3), 1.836 (m, 2H, CH2CH2N+), 3.580 (s, 6H, (CH3)2N+), 3.846–3.814
(t, J = 16 MHz, 2H, CH2N+), 5.213 (s, 2H, PhCH2N+), 7.405 (s, 3H, Ph), 7.858–7.848 (d,
J = 5, 2H, Ph). ESI-MS: m/z 332.2014 [M+] (calc. for [C23H42N]+ = 332.61). –ve ESI-MS:
m/z 389.6122 [M-1 + NH4Cl] (calc. for [PtCl4 + NH4Cl]=390.381). UV/Vis in DMF: λmax [ɛ
(dm3molꢁ1cmꢁ1)] = 260 (1269), 335 (106), 400 (67) nm, in DMSO: water (1 : 1): λmax [ɛ
(dm3molꢁ1cmꢁ1)] = 270 (1577.5), 335 (239.5) nm, in DMSO: phosphate buffer (1 : 1): λmax
[ɛ (dm3molꢁ1cmꢁ1)] = 255 (1184), 305 (187.5) nm.
2.3. UV/Vis spectroscopy
Electronic spectra were recorded with a Spectro 2060 plus model UV/Vis spectrophotome-
ter from 200 to 600 nm using 1 cm path length cuvette. DMF was used for solution prepa-
ration. The stability of compounds was determined by preparing a solution in DMSO/
water and DMSO/phosphate buffer of pH 7.2. Buffer solution was prepared by adding
70 mL 0.1 M aqueous NaOH solution into 0.1 M aqueous KH2PO4 solution. The pH of the
resultant buffer was checked with RS-232 modeled Cyber scan pH 2100, EUTECH pH
meter instrument. Their concentration for the UV study with DMF, DMSO/water and
DMSO phosphate buffer was kept constant at 2 ꢂ 10ꢁ3 M.
2.4. Conductance measurement
Conductance was measured with a LABINDIA, PICO + model conductivity meter at 25 °C
for 1 ꢂ10ꢁ3 M solution in DMF. Aqueous 0.1 M (12.88 mS/cm), 0.01 M (1.413 mS cmꢁ1
)
and 0.001 M (147 μS cmꢁ1) KCl solutions were used for calibration standard.
2.5. Zeta potential and particle size measurement
A Microtrac Zetatrac, U2771, Dynamic Light Scattering equipment was used for solution
prepared in DMSO. Set-zero was done with DMSO, and then, 15% MBK8 in DMSO was

Tetraammoniumplatinate
555
filled in the sample holder. For Zeta potential and particle size standard, an auto-suspended
solution of alumina suspension (400206-100) was used.
2.6. SEM and EDX analysis
SEM images were obtained with EVO18-18-69 model ZEISS SEM. The sample was
adhered to carbon tape and then made conductive in a coater chamber of gold (80%) and
palladium (20%) by plasma sputtering. EDX analysis was made for qualitative analysis of
the elements (except H, due to an absence of L electron) in compounds with a EVO18-18-
69 model ZEISS SEM.
2.7. Differential Scanning Calorimetry (DSC)
Heat-holding capacity was determined with an Intracooler Perkin-Elmer DSC-6000 in an
aluminum sample holder with Pyris manager software. The 2 mg sample was taken for
measurement at 5 °C minꢁ1 heating and cooling rate. Aluminum pen was used as reference
and also as sample holder.
2.8. Atomic force microscopy analysis
Topographical studies were carried out with a XE-76 model, advanced scanning probe,
Park system corp. Atomic force microscopy (AFM) technique was used with silicon canti-
lever in noncontact taping mode. The 0.1 M solution in chloroform was put on a 10 ꢂ 2.5
cm2 glass slide, and the chloroform was evaporated in vacuum at room temperature for
half an hour. On complete evaporation, it was scanned for topography under set phase and
amplitude.
2.9. Gas adsorption
Surface area, pore size volume, and pore size distribution determinations were made by
sorptomatic with multilayer adsorption with Brunauer, Emmett and Teller (BET) theory,
Thermo Scientific (Surfer). MBK8 (478.3 mg) was poured in a burette for degassing over-
night at 90 °C with 10ꢁ2–10ꢁ3 torr vacuum. Then, the burette was attached to a liquid N2
containing Dewar flask at 1.5 bar N2 gas pressure.
2.10. Antioxidant activities
Antioxidant activities were assessed on the basis of free radical scavenging of stable 1-2,5-
diphenyl-2-picrylhydrazyl (DPPH). Diluted solutions were prepared in DMSO/water (1 : 1).
DPPH (0.002% prepared in DMSO/water, 1 mL) was mixed with 1.5 mL of compound and
shaken vigorously and kept in the dark for 30 min. The absorbance was measured at
517 nm with a Spectro 2060 plus model UV/Vis spectrophotometer. Radical-scavenging
activity was measured as a decrease in absorbance of DPPH. A lower absorbance of reac-
tion mixture indicated higher free radical-scavenging activity which was calculated with
the following formula:

556
R.K. Ameta et al.
Scavenging=activity % ¼ ðA0 ꢁ AS=A0Þ ꢂ 100
with AS absorbance of DPPH with a test compound and A0 absorbance of DPPH without a
test compound (control). Data for antioxidation are presented as means SD of three deter-
minations.
2.11. Biological evaluation
The synthesized compounds were screened for their antibacterial activities against human
pathogenic bacteria, viz. Gram-negative (Escherichia coli; ATCC 25922) and Gram-posi-
tive (Staphylococcus aureus; ATCC 33591) bacterial strains by Kirby Beurs Disc Diffusion
Method using DMSO as solvent at 200 μg mLꢁ1 on Mueller Hinton Agar media. The zone
of inhibition was measured in millimeter (mm) after 24 h incubation at 37 °C and pH 7.4.
The zones of inhibition were compared with the standard drugs ampicillin (10 μg) and gen-
tamycin (10 μg) which had resistant and sensitive 6 28, P28 and 612 and P15, respec-
tively. Discs with only DMSO were used as positive control.
3. Results and discussion
3.1. Synthesis and characterization
Synthesis of MBK was conducted with potassium tetrachloroplatinate (K2PtCl4) and N-
alkyl-N-benzyl-N,N-dimethyl ammonium chloride (BKC, n = 8, 10, 12, and 14 alkyl side
chain) in aqueous solution. On mixing and continuous vigorous stirring of BKC and
K2PtCl4 producing N-alkyl-N-benzyl-N-N-dimethyl ammonium cation and divalent tetra-
chloroplatinate anion resulted in light pink MBK after 24 h. Four different 99% pure MBK
compounds were synthesized with 95% yield (scheme 1). The compounds were not soluble
in water, ethanol, and methanol, confirming strong ionic bonds.
The –CH3- and –CH2-stretching bands in FTIR of MBK compounds are at 3071–
2977 cmꢁ1 and 2955–2851 cmꢁ1, respectively. At 895–871 cmꢁ1, aromatic –CH were con-
firmed. A peak for mono substituted benzene (PhCH2–) was noted at 789–704 cmꢁ1. The
C–N bending vibrations were at 1218 cmꢁ1. The platinum nitrogen ionic bond vibration
was identified at 524–479 cmꢁ1 [71–74].
1
In H NMR of MBKs, H3, H4, and H5 (scheme 1) of the benzene ring of N-alkyl-N-
benzyl-N,N-dimethyl ammonium produced a singlet at δ = 7.405–7.439 ppm and (H2 and
H6 (scheme 1) appeared at 7.858–7.827 ppm as doublets with J = 4.5 MHz. Two benzyl –
CH2 protons appeared at 5.21 ppm as a singlet. Six protons of two –CH3 on quaternary
nitrogen showed a singlet at 3.597 ppm. The 2H protons of CH2CH2N+ showed a triplet at
3.85–3.81 with J = 16 MHz, due to deshielding by the more electronegative nitrogen.
The 2H of CH2CH2N+ showed a multiplet at 1.86–1.83 ppm, due to an influence of 2H
placed nearest to nitrogen (CH2N+), and from alkyl protons (8H, 10H, 12H, 14H of MBK8,
MBK10, MBK12, MBK14, respectively) with a broad multiplet at 1.316–1.270 ppm. The
2H of CH2CH2CH3 appeared at 1.459–1.382 ppm with multiplets. The –CH3 of the alkyl
chain showed a triplet at 0.914–0.864 ppm with J = 13 and 13.5 MHz. The MBKs have
ionic bonds; thus the ESI +ve mass spectra showed cationic M+ mass peaks, 248.2390,
276.2703, 304.3025, and 332.2014 for [C17H30N]+, [C19H34N]+, [C21H38N]+, and

Tetraammoniumplatinate
557
H2
C
CH3
Cl-
N+
K2PtCl4
+
2
CnH2n+1
BKC
CH3
Potassium tetrachloroplatinate
n= 8, 10, 12, 14
H2O
-2 KCl
4
5
3
6
2
1
CH3
H3C
H3C
Cl
Cl
H2C
N+
Pt2-
N+
CH2
CH
3 Cl
Cl
bis (benzyldimethylalkylazaniumyl) tetrachloroplatinumdiuide
Scheme 1. Reaction scheme 1.
[C23H42N]+, respectively. In the negative mode, they showed M-1 peak having m/z = 389.61
for PtCl4 with an additive mass of NH4Cl (m/z = 53.491), due to use of aqueous ammonium
acetate as mobile phase in the negative mode.
3.2. XRD analysis
XRD powder pattern peaks for MBK8 shown in Supplementary material indicate the crystal-
line nature of the compound. The highest intensity peak was evaluated at 5.65h angle with
15.6293A d-spacing value. The full width half maximum value for this peak was 0.1233.
3.3. Absorption spectroscopy
UV/Vis spectra were recorded in DMF for 2 ꢂ 10ꢁ3 molar solution from 200 to 600 nm.
The compounds and K2PtCl4 exhibit three λmax at 260, 335, and 400 nm (figure 1) and the
2ꢁ
same patterns of spectra with K2PtCl4 showed PtCl4 in the compounds. The absorption
1
1
spectrum consists of a band at 400 nm, assigned as A1g → A2g (dxy ! dx2ꢁy2 ) transition
[75]. The other d-d bands occurred at higher energies and interacted with quaternary ammo-
nium transitions. Their solutions in DMF produced the same λmax, but decreased in intensity,

558
R.K. Ameta et al.
Figure 1. UV/Vis spectra of MBKs in DMF.
and indicated no formation of bond between platinum and nitrogen. A decrease in absor-
bance inferred charge–charge interaction between Pt2ꢁ and positively charged quaternary
nitrogen similar to Magnus salts [19]. To investigate whether the solid state structure is
retained in solution, the UV/Vis spectral behavior was investigated in DMSO/water as well
as in DMSO/phosphate buffer (pH = 7.2) for 2 ꢂ 10ꢁ3 M (figures 2 and 3). The overall pat-
terns for spectra corresponding to each compound were similar. The compounds including
K2PtCl4 showed two λmax at 270 and 335 in DMSO/water (figure 2) and at 260 and 305 in
DMSO/phosphate buffer (figure 3). The same λmax inferred stability, but a decrease in absor-
bance of K2PtCl4 also informed a charge–charge interaction between Pt2ꢁ and the positively
charged quaternary nitrogen in DMSO/water and DMSO/phosphate. Such interactions prove

Tetraammoniumplatinate
559
Figure 2. UV/Vis spectra of MBKs in DMSO-water.
that the compounds have assembled into supramolecular frameworks with
½ðC6H5CH2NðCH3Þ ðCnH2nþ1Þꢀþ and [PtCl4]2ꢁ (figure 4), similar to the Magnus salt where
2
2
[Pt(NH3)4]2+ and [PtCl4]2ꢁ units assemble into a supramolecular structure [19].
3.4. Molar conductivity analysis
Low molar conductivities (table 1) were noted, although the compounds are ionic in
nature. The Columbic attraction between cationic quaternary ammonium and anionic
tetrachloroplatinate is very strong (figure 4), restricting free movement of ions. The
compounds exhibited very similar low molar conductivities due to their low electrolytic
tendency as evidence of cation–anion interaction (supramolecular interaction).

560
R.K. Ameta et al.
Figure 3. UV/Vis spectra of MBKs in DMSO-phosphate buffer.
3.5. Zeta potential and particle size measurement
Zeta potential and particle size distribution were determined with DLS for 15% MBK8
in DMSO and showed 4.56 mv zeta potential with positive polarity, indicating low
quantified magnitude of electrical charges at the double layer. Comparing the average
value of Zeta potential from the literature [76], MBK8 showed a strong agglomeration
as existence of stability. Their distribution is illustrated (Supplementary material) where
the particles of 6540 nm are passed 100% through a zero% channel, implying maxi-
mum size of 6540 nm and the particle surface obtained as mean area diameter is
706 nm. It indicated an average of particles which is less weighed than the mean
volume diameter of coarse particles. An average particle size related to population and

Tetraammoniumplatinate
561
Figure 4. Supramolecular assembly of MBK units.
Table 1. Conductance, molar conductance, and DSC data of the compounds.
Compound C/M
Con (μS cmꢁ1
)
Ω )
ꢁ1 m2 molꢁ1 Onset (°C) Peak (°C) Area (mJ) ΔH (J gꢁ1
MBK-8
1 ꢂ10ꢁ3
52.19
54.17
52.98
52.3
5.219
5.417
5.298
5.230
117.43
115.53
86.68
120.03
117.25
88.69
88.677
182.484
86.194
96.929
54.403
MBK-10
MBK-12
MBK-14
1 ꢂ10ꢁ3
1 ꢂ10ꢁ3
1 ꢂ10ꢁ3
88.8969
47.8867
55.3878
65.66
72.65
volume distribution was measured as mean number diameter as 316.0 nm. A mean
diameter of their intensity distribution reflects a relationship of detected light signal at
2106 nm. The 8.50 M2/CC, specific surface area had depicted smooth, solid and spheri-
cal particles. The 1723, a standard deviation, described a width of measured particles
size distribution; it did not provide an indication of statistical error.
3.6. SEM and EDX analysis
SEM determined a morphological investigation within 6 μm scanning area; here, we men-
tion only the MBK8 image (Supplementary material). The scanning images showed the

562
R.K. Ameta et al.
same and single kinds of particles. In EDX analysis, the residue observed on the stub only
contained strong signals of platinum (Pt), chlorine (Cl), nitrogen (N), and carbon (C) (Sup-
plementary material). No peaks for potassium of K2PtCl4 (starting material) or any others
indicate 100% purities. In EDX spectra, three lines were obtained for platinum, for chlo-
rine two and one each for carbon and nitrogen. For Pt, the three lines could be explained
that it has a larger size with electrons in shells having principle quantum numbers 1–6.
The first line has energy near 10 keV due to the electron vacancy in the M shell filled by
an electron of the N shell and Mα radiation emitted. Also, a second line at slightly more
than 2 keV depicts vacancy of the L shell which is filled by M shell electron and Lα radia-
tion emitted. The same Lα radiation is emitted for chlorine at 3 keV. Lines for Pt, Cl, C,
and N obtained below 1 keV due to K electron vacancies are filled by L electron and Kα
radiations emitted.
3.7. Thermal analysis
DSC analyzes changes in physical properties on increasing temperature with time [77–80],
widely used for inspection of polymer, biopolymer, and pharmaceuticals. On temperature
change, disruption of molecular forces takes place which depict the nature and stabilization
of the compounds [81]. Our compounds showed an effect of alkyl chain on the onset or
melting point peak and fusion enthalpy (Supplementary material). Augmentation in alkyl
chain with –CH2CH3 group decreased onset point by 21.02 °C from MBK12 to MBK14,
while the difference from MBK8 to MBK10 is 1.90 °C (table 1). On increasing the mass
of the compounds by –CH2CH3, the melting point is decreased. A decrease in onset
indicates sensitiveness and cohesivity due to decrease with augmentation of alkyl chain.
The ΔH values indicate heat-holding capacities which are MBK10 > MBK14 > MBK8 >
MBK12, with maximum value for MBK10. No consequential effect of alkyl chain on ΔH
values explains the total heat energy uptake after a suitable transition [82]. A maximum
area of MBK10 inferred the strongest cohesivity.
3.8. Topographical studies
Topographical images taken with AFM of a thin film coated on a glass slide in 30 μm scan
area showed similar images. The image of MBK8 is analyzed (figure 5). An orientation in
arrays of coordination planes in ½ðC6H5CH2NðCH3Þ ðCnH2nþ1Þꢀþ [PtCl4]2ꢁ units were
2
2
shown from AFM. Line analysis of topographic image at ꢁ231.84 and 236.91 nm showed
minimum and maximum values, respectively, in the selected line (table 2). Average value
of minimum and maximum is 2.124 nm, a mid value. The root mean square of roughness
and average roughness area were 104.133 and 87.345 nm, respectively. The point average
roughness area was calculated by 10-point average roughness and was 282.015 nm. Skew-
ness (Rsk) and kurtosis (Rku) values of a line are also shown in table 2, for spikiness of a
sample surface.
3.9. Gas adsorption
Sorption isotherms for N2, used in specific surface area and pore structure measurements,
have been accurately determined on a number of mineral, oxide, and metallic salt systems

Tetraammoniumplatinate
563
Figure 5. AFM topographic image of MBK8.
Table 2. AFM data for MBK8.
Line
Red
Min
(nm)
Max
(nm)
Mid
(nm)
Mean
(nm)
Rpv
(nm)
Rq
(nm)
Ra
(nm)
Rz
(nm)
Rsk
Rku
ꢁ231.843
236.091
2.124
0
467.935
104.133
87.345
282.015
0.045
2.487
[83]. Specific surface area of MBK8 is obtained by BET, where isotherm (Supplementary
material) and pore size distribution (Supplementary material) illustrate that the extent of
apparent cross-sectional areas for adsorbed nitrogen vary with surface structure, exchange-
able ion, and microporosity. An isotherm obtained for nitrogen on MBK8 surface, where
the value of the BET area for the MBK8 was 6.286992 m2 gꢁ1, and the pore size distribu-
tion was also obtained for MBK8 (table 3). Specific surface area and pore structure of
MBK8 are two of its most important characteristics in determining both its chemical and
physical interactions with its surroundings. Experimental studies of such reactions refer
back to a unit area basis. Similarly, interpretation of physical properties like swelling
behavior, aggregate structure formation, and permeability requires an accurate measurement
of specific surface area and pore structure.
3.10. Antioxidant activities
Activities were evaluated by free radical-scavenging effect of stable, DPPH as per the liter-
ature procedure [84] with slight modifications. The percent scavenging activity of the
MBKs was determined in a concentration-dependent manner in comparison to DPPH free
radical absorption at 517 nm [85,86] in DMSO/water of 0.440–0.445 absorbance maxi-
mum. The addition of synthesized compounds with various concentrations from 0.01 to
4 μg mLꢁ1 showed a decrease in absorption, indicating antioxidant activities (figure 6).

564
R.K. Ameta et al.
Table 3. BET data for MBK8.
Surface area calculation
Calculation method
P/P0
BET
0.007–0.306
1.438074
6.256992
0.9837337
7.595982
0
Monolayer volume (ncc gꢁ1
)
Specific surface area (m2 gꢁ1
Correlation factor
)
C value of BET equation
Pore-specific volume (cm3 gꢁ1
Pore-specific volume at P/P0
Pore size calculation
)
0.9910728
Calculation method
BJH
Pore size range (diameter)
0.31–1.0
0.058
2.784302
782.7239
Cumulative volume (cm3 gꢁ1
Maximum diameter (nm)
Average diameter (nm)
)
Figure 6. Free radical scavenging activities of MBKs.
MBK8 and MBK10 showed maximum antioxidant nature at 0.5 μg mLꢁ1 with 44.94 and
41.43%, respectively, while MBK12 showed at 0.02 μg mLꢁ1 with 44.15%. MBK14
showed almost 50% of scavenging activity at 0.02 μg mLꢁ1 referred to as its EC50 value.
3.11. Biological evaluation
Biological evaluation was made by Kirby Beurs Disc Diffusion Method with the literature
procedure [86,87]. Due to quaternary nitrogen, MBKs gave best response against Gram-
negative E. coli and Gram-positive Staphylococci excepting MBK14 (table 4). The
MBK12 has 100% zone of inhibition in comparison with standard for Staphylococci, while
MBK8 and MBK10 have almost equal zone of inhibitions with 86.66 and 80% against

Tetraammoniumplatinate
Table 4. Antibacterial activities for MBKs.
565
Compound (200 μg)
Zone of inhibition on Staphylococci (mm)
Zone of inhibition on E.coli (mm)
MBK8
MBK10
MBK12
MBK14
26
26
30
19
30
24
24
19
00
20
Control (standard)
Staphylococci and E. coli, respectively. MBK14 is not effective against E. coli. The bio-
logical evaluation inferred that with an augmentation in the alkali chain, the MBKs
showed greater activity against positive organisms and less against negative organisms.
4. Conclusion
Synthesis and characterization of tetraammoniumplatinates derived from BKC and potas-
sium tetrachloroplatinate were stable under physiological conditions. The platinum-based
ionic supramolecular complexes have been obtained through a simple approach of using
water as medium at NTP. UV/Vis studies using different media show stability of the com-
pounds. Powder XRD data confirm crystalline nature of the synthesized compounds. The
molar conductivities and zeta potential confirmed their ionic supramolecular framework. A
larger surface area of MBK8, 6.29 ꢂ 104 cm2 gꢁ1, obtained by BET is important data. The
sharper onset temperature areas in DSC data revealed that the complexes have a fixed lat-
tice which does melt at a similar temperature. The compounds exhibited good antimicro-
bial and antioxidant activities, with best for MBK14 and MBK12. Diffusion coefficients,
structural modifications, and other biological studies to determine their role on the apopto-
tic and proliferate pathways in tumor cell lines continue. Since the complexes belong to a
class of supramolecules, intramolecular multiple force theory, and friccohesity could be
models for their physicochemical studies.
Supplementary material
It includes SEM/EDX analysis, particle, and pore size distributions separately.
Acknowledgements
Authors are thankful to the Vice Chancellor, Central University of Gujarat, Gandhinagar,
for financial, infrastructural support, and experimental facilities.
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