Inorganica Chimica Acta 414 (2014) 264–273

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Inorganica Chimica Acta

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Polymeric and cyclic manganese phosphates and phosphinates:Synthesis, spectral characterization and solid-state structures

http://dx.doi.org/10.1016/j.ica.2014.01.0380020-1693/� 2014 Elsevier B.V. All rights reserved.

⇑ Corresponding author. Tel.: +91 22 2576 7163; fax: +91 22 2572 3480/25767152.

E-mail address: rmv@chem.iitb.ac.in (R. Murugavel).

Ramasamy Pothiraja a, Palanisamy Rajakannu a, Pratap Vishnoi a, Ray J. Butcher b, Ramaswamy Murugavel a,⇑a Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, Indiab Department of Chemistry, Howard University, Washington, DC 20059, USA

a r t i c l e i n f o a b s t r a c t

Article history:Received 9 March 2013Received in revised form 14 January 2014Accepted 22 January 2014Available online 17 February 2014

Keywords:PhosphinatesEight-membered ringHydrogen bondingp–p Interactions

Polymeric manganese phosphinates [Mn(ppi)2(bpy)]n (1) and [Mn(ppi)2(phen)]n (2) have been obtainedby treating manganese acetate with phenylphosphinic acid (ppi-H) in the presence of either 2,20-bpy or1,10-phen, respectively. The reaction of preformed precursor [Mn(OAc)(bpy)2](ClO4)(H2O) with phosphi-nic acids or phosphate diesters yield [Mn(L)(bpy)2]2(ClO4)2 (where L-H = dtbp-H = di-tert-butyl hydrogenphosphate (3), dpp-H = diphenyl hydrogen phosphate (4), dppi-H = diphenyl phosphinic acid (5), andppi-H = phenyl phosphinic acid (6)), which are dimeric compounds. Polymers 1–2 and dinuclear cycliccompounds 3–6 have been extensively characterized by analytical and spectroscopic methods and alsoin each case by a single crystal X-ray diffraction study.

� 2014 Elsevier B.V. All rights reserved.

1. Introduction phosphate complexes ex. M-dtbp with interesting architectures

Phosphate glasses are of technological interest due to theirunique properties, such as high thermal expansion coefficient,low glass transition temperature and low softening temperature[1–5]. Hence they are potential candidates for making solid stateelectrolytes, machinable glass ceramics, amorphous semiconduc-tors [6,7], laser glasses, optoelectronic and nuclear waste storagematerials [8,9]. The technological importance of these glasses re-quires a detailed understanding of the molecular and structuralchemistry to design them specifically for a particular application[10–12]. The reaction between a metal ion and a phosphorus acidor its ester has also attracted the attention of inorganic, bioinor-ganic, biological and materials chemists over several decades inview of metal catalyzed phosphate ester hydrolysis, synthesis ofcage-like and extended frame-work metal phosphates [13–20]. Inparticular, there has been a recent upsurge on studies related tothe interaction of phosphate ligands with late transition metal ionssuch as Fe, Co, Ni, Cu, and Zn in view of their relevance to cancertherapy through DNA cleavage and biological activity. Severalmono and dinuclear transition metal complexes incorporatingstructurally and electronically diverse ligands have been investi-gated for this purpose [21–23]. Our recent investigations in thisarea have centered around the synthesis and structural character-ization of a variety of transition metal di-tert-butyl and related

[24–36].Our original interest in this area was exploring the use of di-tert-

butylphosphate complexes of transition metals as precursors forthe preparation of metal phosphate materials in view of the highthermal instability of these complexes. Our latter investigationshave however shown that these complexes are useful model com-pounds for metal catalyzed phosphate-ester hydrolysis reactions[29–36]. For example, simple binary metal-dtbp complexes of thetype [M(dtbp)2]n (M = Mn, Co, Cu, Zn, Cd) serve as excellent molec-ular precursors for the preparation of respective fine-particle met-alphosphate materials [M(PO3)2] at fairly low temperatures [37].Use of ancillary ligands like 2,20-bipyridine and 1,10-phenanthro-line breaks the polymeric complexes to lower oligomers and mono-meric complexes [38], many of which have been found to be usefulmodel compounds for phosphate ester hydrolysis reactions. Contin-uing our studies on metal chemistry of phosphorous acids for theabove reason, we now designed and prepared a series of manganesephosphinates and phosphates which exihibit cyclic and polymericstructures. The results of this investigation are reported herein.

2. Results and discussion

2.1. Synthesis and structural characterization of [Mn(ppi)2(bpy)]n (1)and [Mn(ppi)2(phen)]n (2)

2.1.1. SynthesisThe manganese phosphinates [Mn(ppi)2(bpy/phen)]n (1–2)

have been synthesized from the reaction of Mn(OAc)2�4H2O with

Scheme 1. Synthesis of [Mn(ppi)2(bpy)]n (1) and [Mn(ppi)2(phen)]n (2).

Fig. 1. (a) Molecular structure of [Mn(ppi)2(bpy)]n (1) (top) and (b) polyhedral representation of [Mn(ppi)2(bpy)]n (1) (bottom). (in all cases, hydrogen atoms on phenylgroups and bpy are omitted for clarity).

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ppi-H (phenylphosphinic acid) and 2,20-bipyridine (bpy) or 1,10-phenanthroline (phen) in methanol/ethanol mixture (1:1)(Scheme 1). The products have been isolated as single crystals di-rectly from the reaction mixture in a good yield. Compounds 1and 2 are air- and moisture stable and are soluble in polar organicsolvents.

2.1.2. Spectral characterization of [Mn(ppi)2(bpy)]n (1) and[Mn(ppi)2(phen)]n (2)

Compounds 1 and 2 have been characterized with the aid ofanalytical and spectroscopic studies. The absence of infraredabsorption in the region 2700–2500 cm�1 indicates the completeneutralization of P–OH group. Strong IR bands observed at 1232,1133 and 1056 cm�1 for 1 and 1179, 1132 and 1052 cm�1 for 2indicate the presence of POO and M–O–P linkages [35,38]. Strong

absorption at 2318 cm�1 clearly indicates the presence of P–Hgroup in both cases [39]. The UV–Vis spectra exhibit a band at298 nm for 1 and 294 nm for 2. This can be assigned to the p–p⁄

transition of bpy/phen and phenyl groups. Compound 1 showsemission at 325 nm, when it is excited at 298 nm. When 2 is ex-cited at 294 nm, a strong emission was observed at 365 nm inthe fluorescence spectrum of 2. The room temperature magneticmoment (lfound = 5.71 BM for 1 and 6.22 BM for 2) is consistentwith the high spin d5 configuration of Mn2+ ions.

2.1.3. Molecular structure of [Mn(ppi)2(bpy)]n (1)X-ray diffraction quality yellow single crystals were obtained

when compound 1 was crystallized from methanol/ethanol mix-ture at room temperature. The compound crystallizes in the ortho-rhombic Pbna space group. A part of the polymeric structure of 1 is

Fig. 2. Comparative scheme of structure of [Mn(dtbp)2]n with 1 and 2.

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shown in Fig. 1a. The repeating unit of the polymer contains oneMn2+ ion, two bridging ppi ligands and one chelating bpy as shownin Scheme 1. Thus each octahedral Mn2+ ion is coordinated by fourppi ions and one bpy ligand. Two ppi ligands bridge two neighbor-ing Mn2+ ions, thus forming an 8-membered ring. These rings areconnected to form a one dimensional polymeric structure asshown in the Fig. 1. Since Mn2+ ions are doubly bridged, the ob-served Mn� � �Mn seperation (5.2960(9) Å) is found to lie in betweenthe values found for [Mn(dtbp)2]n where alternating single and tri-ple bridges are found (5.716(2) and 3.946(1) Å, respectively) [29].The comparative scheme of the structures of [Mn(dtbp)2]n and 1is shown in Fig. 2.

2.1.4. Molecular structure of [Mn(ppi)2(phen)]n (2)Yellow single crystals of 2 were obtained in methanol/ethanol

mixture by slow evaporation of the solvent at room temperature.The compound crystallizes in the orthorhombic Pbcn space group.Here again, each octahedral Mn2+ ion is coordinated by four bridg-ing ppi ligands and one phen ligand (Fig. 3). The Mn� � �Mn distanceis comparable to that found in 1 which has a similar structure(Fig. 2) [29]. As found in 1, the Mn-phosphinate Mn2O4P2, 8-mem-bered rings are connected to each other to yield a polymeric struc-ture as shown in the Fig. 3. These 1-D polymers are held togetherthrough (phen)C–H� � �O intermolecular hydrogen bonds (Fig. 3).In addition to hydrogen bonding, p–p stacking between the phen(distance between two phen, 3.845(2) Å) stabilizes the overallstructure. The inter polymeric strand distance (12.024(1) Å) islonger than that (11.060(1) Å) found for 1.

2.1.5. Thermal analysis of polymers 1 and 2Thermogravimetric analysis was carried out for the complex 1

in nitrogen atmosphere. On the basis of weight percentage of stepsin TG curve and weight percentage of various molecular parts withrespect to monomeric unit, it has been proposed that the firstweight loss of 32% in between 100 and 330 �C, is due to the re-moval of bpy. The second weight loss of 16% in between 330 and530 �C, is due to the removal of phenyl group. Further heating of

this compound leads to the third weight loss of 16% at 530–760 �C (Fig. 4). Similarly, the complex 2 shows first weight loss of34.8% in between 250 and 422 �C, due to the loss of phen unit.The second weight loss of 15.1% in the range 423–545 �C, is dueto the removal of a phenyl ring and the third weight loss of15.1% in between 546 and 905 �C, due to the removal of the secondphenyl ring.

2.2. Synthesis and Characterization of [M(L)(bpy)2]2(ClO4)2 (3–6)

2.2.1. SynthesisThe use of [Mn(OAc)(bpy)2](ClO4)(H2O) in the place of

Mn(OAc)2�4H2O, as a source of Mn2+ ion, results in different prod-ucts. Thus the reaction of [Mn(OAc)(bpy)2](ClO4)(H2O) with aphosphate diester or phosphinic acid {(tBuO)2PO2-H (dtbp-H),(PhO)2PO2-H (dpp-H), Ph2PO2-H (dppi-H) and Ph(H)PO2-H (ppi-H)} in methanol resulted in the formation of manganese phos-phates and phosphinates [Mn(L)(bpy)2]2(ClO4)2 {where L = dtbp(3), dpp (4), dppi (5), and ppi (6)} (Scheme 2). In all cases, the reac-tion was carried out under very mild conditions by stirring thereactants in a beaker at room temperature. In most cases, the finalproducts were obtained as single crystals by leaving the reactionflask for crystallization for a few days. The products were foundto be air and moisture stable and they do not melt up to 250 �C.

2.2.2. Spectral characterization of compounds 3–6The analytically pure samples of 3–6 were further characterized

with the aid of spectroscopic techniques. The absence of infraredabsorption in the region 2700–2500 cm�1 indicates the completeneutralization of P–OH group. Strong IR bands observed at 1235,and 1090 cm�1 for 3, 1257, 1159, and 1015 cm�1 for 4, 1246,1158, and 1052 cm�1 for 5 and 1247, 1162 and 1053 cm�1 for 6indicate the presence of POO and M–O–P linkages [35,38]. Strongabsorption at 2320 cm�1 clearly indicates the presence of P–Hgroup in 6. This strong absorption were absent in 3–5 indicatesthe absence of P–H group. The UV–Vis spectra exhibit absorption

Fig. 3. Molecular structure of [Mn(ppi)2(phen)]n (2) (top) and hydrogen bonding pattern of 2 (bottom).

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maxima at 300 nm for 3, 297 nm for 4, 296 nm for 5, and 292 nmfor 6. The observed single absorption around 300 nm could be as-cribed to the p–p⁄ transition of the bpy ligand and/or the aryl ringsof the phosphate ligands. Due to the d5 configuration of Mn2+, thereis no absorption in the visible region of the spectrum. The roomtemperature magnetic moment of manganese phosphates andphosphinates (3–6) is consistent with the high spin d5 configura-tion of Mn2+ ions. The emission spectroscopic characteristics ofall new manganese complexes have been studied in methanolicsolution by exciting the compound in the region of 290–300 nm.A single strong singlet emission was found around 320 nm for allcomplexes.

2.2.3. Molecular structure of [Mn(dtbp)(bpy)2]2(ClO4)2 (3)Yellow single crystals of [Mn(dtbp)(bpy)2]2(ClO4)2 (3) was

crystallized from methanol by slow evaporation. The compoundcrystallizes in the monoclinic P21/n space group. The dtbp ligandsare acting as bidentate bridging ligands, and bridge two Mn ions

(av. Mn–O, 2.088(3) Å) to form a dimer (Fig. 5). Each Mn ion is fur-ther coordinated by two bpy (av. Mn–N, 2.288(2) Å) leading to theformation of distorted octahedral coordination geometry around it.Two perchlorate anions occupy the outer sphere to maintaincharge neutrality. The (Mn)O–P bond distances (av. P–O,1.487(2) Å) are shorter than (C)O–P bond distances (av. P–O,1.588(2) Å) and (Mn)O–P–O(Mn) bond angles (O(2)–P(1)–O(1),118.9(1)�, O(5)–P(2)–O(6), 119.3(1)�) are wider than (C)O–P–O(C)bond angles (O(8)–P(2)–O(7), 106.8(1)�; O(3)–P(1)–O(4),106.7(1)�) [11]. Hydrogen bonds formed by perchlorate anionsand phosphate with bpy, lead to the formation of two dimensionallayers as shown in Fig. 6 (Table S1).

2.2.4. The molecular structure of [Mn(dpp)(bpy)2]2(ClO4)2 (4)The molecular structure of [Mn(dpp)(bpy)2]2(ClO4)2 (4) is simi-

lar to [Mn(dtbp)(bpy)2]2(ClO4)2 (3). Compound 4 crystallizes in tri-clinic P�1 space group with two crystallographically uniquemanganese dimeric units in the asymmetric part of unit cell. One

Fig. 4. TGA trace of [Mn(ppi)2(bpy)]n (1).

Scheme 2. Synthesis of manganese phosphates and phosphinates 3–6.

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of the two dimeric units is shown in the Fig. 7. As in 3, the dppligands bridge two Mn ions and results in the formation of a dimer(Fig. 7). Each Mn ion is further coordinated by two bpy and makesoctahedral coordination geometry around it. The bond lengths andbond angles around manganese ions in this compound are compa-rable to those for the compound 3. The hydrogen bonds present be-tween the perchlorate anions and Mn(1) dimeric unit leads to theformation of two dimensional sheet like structure. In the sameway, the hydrogen bonds present between the perchlorate anionsand Mn(2) dimeric units leads to the formation of two dimensionalsheet like structure (Table S1). These sheets are further connectedthrough hydrogen bonds and leads to the formation of threedimensional arrays as shown in Fig. 7.

2.2.5. The molecular structure of [Mn(dppi)(bpy)2]2(ClO4)2(CH2Cl2)(5)The centrosymmetric compound [Mn(dppi)(bpy)2]2(ClO4)2 (5)

crystallizes (monoclinic C2/c space group) from methanol/ dichlo-romethane mixture at room temperature. In addition to two per-chlorate anions, it also has one dichloromethane in the lattice for

each dimeric unit of manganese. The bond lengths and bond anglesaround manganese ions in this compound are comparable to thosefor the compounds 3 and 4. The cationic part of the complex isshown in Fig. 8. The disordered perchlorate anions and latticedichloromethane in 5 does not permit any detailed discussion ofhydrogen bonding pattern in this molecule.

2.2.6. The molecular structure of [Mn(ppi)(bpy)2]2(ClO4)2 (6)The molecular structure of [Mn(ppi)(bpy)2]2(ClO4)2 (6) is simi-

lar to [Mn(dtbp)(bpy)2]2(ClO4)2 (3), [Mn(dpp)(bpy)2]2(ClO4)2 (4)and [Mn(dppi)(bpy)2]2(ClO4)2 (5). This compound crystallizes incentrosymmetric triclinic P�1 space group from a methanol solutionat room temperature. The bond lengths and bond angles aroundmanganese ions in this compound are comparable to those forthe compounds 3, 4 and 5. The cationic part of the complex isshown in the Fig. 9. The hydrogen bonds present between theperchlorate anions and bpy leads to the formation of twodimensional layers as shown in the Fig. 9 (Table S1). A comparison

Fig. 5. Molecular structure of [Mn(dtbp)(bpy)2]22+ (3) (hydrogen atoms and

perchlorate anions are removed for clarity).

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of some important structural parameters for 3–6 is given in TablesS2 and S3.

3. Conclusions

The choice of starting material (metal source) is determiningthe aggregation and structure of the final metal phosph(in)atecomplex has been demonstrated by taking Mn2+ case as anexample. This study further demonstrates the influence of theperchlorate ion on the nuclearity of the resultant metal phosphateand phosphinates. The replacement of the acetate group in the

Fig. 6. Hydrogen bonding pattern in [Mn(dtbp

mononuclear precursor [Mn(OAc)(bpy)2](ClO4)(H2O) by a phos-phate or phosphinate leads to the formation of dinuclear complex[Mn(L)(bpy)2]2(ClO4)2 in all the cases. However, the replacement ofacetate in Mn(OAc)2�4H2O by phosphinate in the presence of bpyor phen leads to the formation of polymeric [Mn(ppi)2(L)]n

(L = bpy or phen) complexes.

4. Experimental

4.1. Materials and methods

Commercial grade solvents were purified by employing conven-tional procedures and distilled prior to their use. Commerciallyavailable starting materials such as Mn(OAc)2�4H2O (E.Merck), pyr-idine (S.d.Fine-Chem.), 2,20-bipyridine (Lancaster), 1,10-phenan-throline monohydrate (S.d.Fine-Chem.), PCl3 (S.d.Fine-Chem.),tBuOH (S.d.Fine-Chem.), conc. HCl (Merck), NaOH (S.d.Fine-Chem.),diphenyl phosphate (Lancaster), diphenylphosphinic acid (Lancas-ter), phenylphosphinic acid (Lancaster) and NaClO4 (Aldrich) wereused as received. [Mn(O2C2H3)(bpy)2](ClO4)(H2O) [40,41], and(tBuO)2PO2H [42] were synthesized as described previously inthe literature.

Elemental analyses were performed on a Carlo Eraba (Italy)Model 1106 Elemental Analyzer at IIT-Bombay. Infrared spectrawere recorded on a Perkin Elmer FT-IR spectrometer as KBr diluteddiscs. UV–Vis spectra were obtained on Shimdzu UV-260 and UV-160A spectrophotometers. The EPR measurements were madewith a Varian model 109C E-line X-band spectrometer fitted witha quartz Dewar for measurements at 77 K (liquid nitrogen). Thespectra were calibrated using tetracyanoethylene (tcne). Magneticsusceptibility was checked with a PAR vibrating sample magne-tometer. Thermal analyses were carried out on a Perkin Elmer ther-mal analysis system. Fluorescence measurements were carried outusing Perkin Elmer LS 55 fluorescence spectrometer.

)(bpy)2]2(ClO4)2 (3) (viewed down c axis).

Fig. 7. Molecular structure of [Mn(dpp)(bpy)2]22+ (4) (top, perchlorate anions are removed for the clarity) and Hydrogen bonding pattern in [Mn(dpp)(bpy)2]2(ClO4)2 (4)

(bottom, viewed along b-axis).

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4.2. Synthesis of [Mn(ppi)2(bpy)]n (1)

Mn(OAc)2�4H2O (245 mg, 1 mmol) was dissolved in methanol/ethanol mixture (20 mL/20 mL) and bpy (312 mg, 2 mmol) wasadded. To the resulting solution, ppi-H (284 mg, 1 mmol) wasadded and stirred for 5 min and filtered. The filtrate was kept atroom temperature for crystallization. X-ray diffraction qualitycrystals were obtained by crystallizing the compound in metha-nol/CH3CN (1:1) mixture. Yield: 0.42 g (85%). Mp: 212–214 �C.Anal. Calc. for C22H20MnN2O4P2 (Mr = 493.3): C, 53.57; H, 4.09; N,5.68. Found: C, 53.0; H, 3.8; N, 5.6%. IR (KBr, cm�1): 3053 (m),2288 (s), 1594 (m), 1470 (w), 1436 (m), 1232 (vs), 1185 (s), 1133(s), 1056 (vs), 1016 (w), 975 (m), 757 (m), 703 (m). UV–Vis (CH3-

OH, nm, e, cm�1M�1): 298 (4858). Fluorescence: (kex = 298 nm,CH3OH): 325, nm. TGA: Temp. range �C (% weight loss): 150–330

(31.8); 330–530 (15.7); 527–762 (16.0). DSC (�C): 214 (endo);254 (endo); 383 (exo); 554 (endo). lfound = 5.71 BM.

4.3. Synthesis of [Mn(ppi)2(phen)]n (2)

Mn(OAc)2�4H2O (245 mg, 1 mmol) was dissolved in methanol/ethanol mixture (20 mL/20 mL) and phen (396 mg, 2 mmol) wasadded. To the resulting solution, ppi-H (284 mg, 1 mmol) wasadded and stirred for 5 min and filtered. The filtrate was kept atroom temperature for crystallization. Yield: 0.26 g (50%). Mp:267 �C. Anal. Calc. for C24H20MnN2O4P2 (Mr = 517.3): C, 55.72; H,3.90; N, 5.42. Found: C, 55.5; H, 3.6; N, 5.6%. IR (KBr, cm�1):3050 (m), 3014 (w), 2319 (s), 1620 (w), 1511 (m), 1427 (m),1229 (s), 1179 (s), 1133 (s), 1051 (s), 1019 (w), 987 (m), 846 (m),767 (w), 749 (m), 727 (m), 702 (s). UV–Vis (CH3OH, nm, e,

Fig. 8. Molecular structure of [Mn(dppi)(bpy)2]22+ (5) (perchlorate ions, CH2Cl2 and

hydrogen atoms on bpy and phenyl groups are removed for the clarity).

Fig. 9. Molecular structure of [Mn(ppi)(bpy)2]22+ (6) (top, perchlorate solvent molecule wa

(bottom).

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cm�1M�1): 294 (13241). Fluorescence: (kex = 294 nm, CH3OH):365, nm. TGA: Temp. range �C (% weight loss): 250–422 (34.8);423–545 (15.1); 546–905 (15.1). DSC (�C): 281 (endo); 338 (endo);419 (endo); 563 (endo); 600 (endo). lfound = 6.22 BM.

4.4. Synthesis of [Mn(dtbp)(bpy)2]2(ClO4)2 (3)

[Mn(OAc)(bpy)2](ClO4)(H2O) (543 mg, 1 mmol) was dissolvedin methanol (40 mL) and dtbp-H (210 mg, 1 mmol) was added.The solution was stirred for 10 min and filtered. The filtrate wascrystallized at room temperature to obtain diffraction quality crys-tals. Yield: 0.65 g (96%). Mp:>220 �C. Anal. Calc. for C56H68Cl2Mn2-

N8O16P2 (Mr = 1351.9): C, 49.75; H, 5.07; N, 8.29. Found: C, 50.3;H, 5.2; N, 8.3%. IR (KBr, cm�1): 3076 (w), 2975 (m), 2932 (w),1597 (m), 1477 (m), 1439 (m), 1381 (w), 1235 (s), 1090 (vs), 988(s), 827 (w), 767 (m), 727 (w), 616 (m). UV–Vis (CH3OH, nm, e,cm�1M�1): 300 (10607). Fluorescence: (kex = 300 nm, CH3OH):326, nm. TGA: Temp. range �C (% weight loss): 120–189 (23.2,�2 bpy); 190–274 (16.6, �4 isobutene); 275–693 (32.5). DSC(�C): 182 (endo); 287 (exo); 306 (endo). lfound = 6.49 BM.

s removed for clarity) and Hydrogen bonding pattern in [Mn(ppi)(bpy)2]2(ClO4)2 (6)

Table 1Crystal data for compounds 1–6.

Compound 1 2 3 4 5 6*

Indentification code rp406a rp407 mur66 Pothi-ICA-4 rp541 Pothi-ICA-6Formula C22H20MnN2O4P2 C24H20MnN2O4P2 C56H68Cl2Mn2N8O16P2 C64H52Cl2Mn2N8O16P2 C65H54Cl4Mn2N8O12P2 C52H44Cl2Mn2N8O12P2

Formula weight 493.28 517.30 1351.90 1431.86 1452.78 1215.67Temperature (K) 293(2) 213(2) 133(2) 150(2) 213(2) 150(2)Wavelength (Å) 0.71073 0.71073 0.71073 0.71073 0.71073 0.71073Crystal system orthorhombic orthorhombic monoclinic triclinic monoclinic triclinicSpace group Pbcn Pbcn P21/n P�1 C2/c P�1a (Å) 23.052(2) 23.610(3) 17.5035(6) 12.603(5) 23.291(2) 8.724(9)b (Å) 11.061(2) 12.024(2) 17.7017(5) 13.807(5) 12.109(1) 11.717(2)c (Å) 8.562(2) 7.776(1) 21.3248(8) 19.125(5) 25.398(3) 14.518(2)a (�) 90 90 90 81.629(5) 90 67.97(3)b (�) 90 90 101.940(3) 81.018(5) 111.60(1) 87.31(4)c (�) 90 90 90 76.595(5) 90 88.24(5)Volume (Å3) 2183.1(8) 2207.4(5) 6464.4(4) 3176.8(2) 6660(1) 1374(2)Z 4 4 4 2 4 1Dcalc (Mg m�3) 1.501 1.557 1.389 1.497 1.449 1.469Crystal size (mm3) 0.43 � 0.35 � 0.28 0.5 � 0.4 � 0.3 0.30 � 0.20 � 0.20 0.2 � 0.09 � 0.04 0.4 � 0.3 � 0.3 0.35 � 0.17 � 0.06Absorption coefficient

(mm�1)0.783 0.779 0.593 0.603 0.655 0.703

Data/restraints/parameters

1924/0/145 1746/0/154 11138/0/775 11084/0/847 5237/181/427 4769/0/369

Goodness-of-fit on F2 1.174 1.045 1.036 0.895 1.054 1.061R1 [I > 2r(I)] 0.0556 0.0362 0.0417 0.0498 0.0491 0.1392R2 [I > 2r(I)] 0.1139 0.0901 0.1080 0.1461 0.1416 0.3745

* Poor quality crystals-repeated attempts failed to improve the diffraction quality.

272 R. Pothiraja et al. / Inorganica Chimica Acta 414 (2014) 264–273

4.5. Synthesis of [Mn(dpp)(bpy)2]2(ClO4)2 (4)

To the methanolic solution of [Mn(OAc)(bpy)2](ClO4)(H2O)(543 mg, 1 mmol in 40 mL), dpp-H (250 mg, 1 mmol) was addedand stirred for 10 min. The resultant solution was filtered andthe filtrate was crystallized at room temperature to obtain X-raydiffraction quality crystals. Yield: 0.60 g (84%). Mp: 267–270 �C.Anal. Calc. for C64H52Cl2Mn2N8O16P2 (Mr = 1431.9): C, 53.68; H,3.66; N, 7.83. Found: C, 53.3; H, 3.5; N, 7.5%. IR (KBr, cm�1):3070 (w), 1595 (m), 1576 (w), 1489 (m), 1474 (w), 1440 (s),1315 (w), 1288 (w), 1268 (s), 1257 (m), 1202 (m), 1159 (w),1107 (vs), 1015 (m), 935 (m), 894 (w), 756 (s), 738 (w), 692 (w),648 (w), 623 (m). UV–Vis (CH3OH, nm, e, cm�1M�1): 97 (19090).Fluorescence: (kex = 297 nm, CH3OH): 325, nm. TGA: Temp. range�C (% weight loss): 215–289 (10.4); 290–372 (50.8); 373–897(18.2). DSC (�C): 226 (endo); 351 (exo). lfound = 9.72 BM.

4.6. Synthesis of [Mn(dppi)(bpy)2]2(ClO4)2(CH2Cl2) (5)

dppi-H (218 mg, 1 mmol) in CH2Cl2 (15 mL) was reacted with[Mn(OAc)(bpy)2](ClO4)(H2O) (543 mg, 1 mmol) dissolved in meth-anol (40 mL). The solution was stirred for 10 min and filtered. Thefiltrate was crystallized at room temperature to obtain diffractionquality crystals. Yield: 0.62 g (85%). Mp:>275 �C. Anal. Calc. for C65-

H54Cl4Mn2N8O12P2 (Mr = 1452.8): C, 53.74; H, 3.75; N, 7.71. Found:C, 53.8; H, 3.6; N, 7.4%. IR (KBr, cm�1): 3059 (w), 1594 (m), 1575(w), 1489 (w), 1473 (m), 1439 (s), 1315 (w), 1246 (w), 1198 (s),1158 (w), 1134 (s), 1096 (vs), 1052 (s), 1013 (m), 772 (w), 760(m), 738 (w), 724 (m), 699 (w), 623 (w). UV–Vis (CH3OH, nm, e,cm�1 M�1): 296 (21367). Fluorescence: (kex = 296 nm, CH3OH):324, nm. TGA: Temp. range �C (% weight loss): 193–411 (53.3);412–597 (15.6); 598–896 (7.3). DSC (�C): 354 (exo). lfound = 8.60BM.

4.7. Synthesis of [Mn(ppi)(bpy)2]2(ClO4)2 (6)

[Mn(OAc)(bpy)2](ClO4)(H2O) (543 mg, 1 mmol) was dissolvedin methanol (40 mL) and ppi-H (142 mg, 1 mmol) in CH2Cl2

(15 mL) was added. The solution was stirred for 10 min and fil-tered. The filtrate was crystallized at room temperature to obtaindiffraction quality crystals. Yield: 0.55 g (90%). Mp: 256–258 �C.Anal. Calc. for C52H44Cl2Mn2N8O12P2 (Mr = 1215.7): C, 51.37; H,3.65; N, 9.22. Found: C, 51.2; H, 3.5; N, 8.9%. IR (KBr, cm�1):3113 (w), 3070 (w), 3051 (w), 2320 (m), 1602 (m), 1575 (w),1566 (w), 1492 (w), 1475 (m), 1439 (s), 1316 (w), 1247 (w),1194 (s), 1162 (m), 1135 (s), 1090 (vs), 1053 (s), 1015 (m), 976(m), 922 (w), 770 (s), 747 (w), 738 (w), 705 (w), 692 (w), 649(w), 625 (m). UV–Vis (CH3OH, nm, e, cm�1M�1): 292 (30188). Fluo-rescence: (kex = 292 nm, CH3OH): 324, nm. TGA: Temp. range �C (%weight loss): 100–284 (10.9); 285–406 (35.2); 407–597 (14.5),598–893 (11.4). DSC (�C): 310 (exo); 369 (exo). lfound = 8.15 BM.

4.8. X-ray crystallography

A suitable crystal of each compound was used for the diffractionstudies on an automated diffractometer (Oxford Xcalibur CCD dif-fractometer for 1, 2, and 5; Bruker CCD diffractometer for 3; RigakuSaturn CCD 724 + diffractometer for 4 and 6). The structure solu-tion was achieved by direct methods as implemented in SHELXS-97[43]. Final refinement of the structures was carried out using fullleast-squares methods on F2 using SHELXL-97 [44]. Other details per-taining to data collection, structure solution, and refinement are gi-ven in Table 1. Due to extremely poor quality of the crystals forcompound 6, good diffraction data could not be obtained. The bestR1 obtained from various batches of crystals is 14%.

Acknowledgement

This work was supported by DST, New Delhi. RM thanks DAE fora DAE-BRNS Outstanding Investigator Award, which enable thepurchase of a single crystal diffractometer.

Appendix A. Supplementary material

Crystallographic data (excluding structure factors) for 1–6 havebeen deposited with the Cambridge Crystallographic Data Centre

R. Pothiraja et al. / Inorganica Chimica Acta 414 (2014) 264–273 273

as supplementary publication no. CCDC 922087-922092. Copies ofthe data can be obtained, free of charge, on application to CCDC, 12Union Road, Cambridge CB2 1EZ, UK: http://www.ccdc.cam.ac.uk/cgi-bin/catreq.cgi, e-mail: data_request@ccdc.cam.ac.uk, or fax:+44 1223 336033. Supplementary data associated with this articlecan be found, in the online version, at http://dx.doi.org/10.1016/j.ica.2014.01.038.

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