کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1230777 1495199 2017 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Novel organic NLO material bis(N-phenylbiguanidium(1+)) oxalate – A combined X-ray diffraction, DSC and vibrational spectroscopic study of its unique polymorphism
ترجمه فارسی عنوان
مواد آلی جدید BIS مواد NLO (N-phenylbiguanidium (1+)) اگزالات - یک ترکیب پراش پرتو X، DSC و مطالعه طیف ارتعاشی پلی مورفیسم منحصر به فرد خود
کلمات کلیدی
نمک N-فنیل بایگانیاید؛ پراش اشعه ایکس؛ طیف سنجی ارتعاشی؛ پلیمورفیسم؛ تولید هارمونیک دوم؛ رفتار حرارتی
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
چکیده انگلیسی


• The three polymorphic modifications (I, II, III) of bis(N-phenylbiguanidium(1+)) oxalate were prepared and characterised.
• The phases (I) and (II) differ not only in crystal packing and symmetry but also in their H-bonds characteristics.
• The detailed study explains the nature of the reversible isostructural phase transformation between phases (II) and (III).

Three polymorphic modifications of bis(N-phenylbiguanidium(1+)) oxalate are reported, and their characterization is discussed in this paper. The non-centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (I), which was obtained from an aqueous solution at 313 K, belongs to the monoclinic space group Cc (a = 6.2560(2) Å, b = 18.6920(3) Å, c = 18.2980(5) Å, β = 96.249(1)°, V = 2127.0(1) Å3, Z = 4, R = 0.0314 for 4738 observed reflections). The centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (II) was obtained from an aqueous solution at 298 K and belongs to the monoclinic space group P21/n (a = 6.1335(3) Å, b = 11.7862(6) Å, c = 14.5962(8) Å, β = 95.728(2)°, V = 1049.90(9) Å3, Z = 4, R = 0.0420 for 2396 observed reflections). The cooling of the centrosymmetric phase (II) leads to the formation of bis(N-phenylbiguanidium(1+)) oxalate (III) (a = 6.1083(2) Å, b = 11.3178(5) Å, c = 14.9947(5) Å, β = 93.151(2)°, V = 1035.05(8) Å3, Z = 4, R = 0.0345 for 2367 observed reflections and a temperature of 110 K), which also belongs to the monoclinic space group P21/n. The crystal structures of the three characterized phases are generally based on layers of isolated N-phenylbiguanidium(1 +) cations separated by oxalate anions and interconnected with them by several types of N-H...O hydrogen bonds. The observed phases generally differ not only in their crystal packing but also in the lengths and characteristics of their hydrogen bonds. The thermal behaviour of the prepared compounds was studied using the DSC method in the temperature range from 90 K up to a temperature near the melting point of each crystal. The bis(N-phenylbiguanidium(1+)) oxalate (II) crystals exhibit weak reversible thermal effects on the DSC curve at 147 K (heating run). Further investigation of this effect, which was assigned to the isostructural phase transformation, was performed using FTIR, Raman spectroscopy and X-ray diffraction analysis in a wide temperature range.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy - Volume 170, 5 January 2017, Pages 256–266
نویسندگان
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