Table 1: Comparison of the experimental IR and Raman spectra with the vibrational frequencies calculated for the twisted and planar forms of the PQ dimer.

Calculate d a Observed Assignmen t d
f r e q u e n c y e (cm−1) f r e q u e n c y f (cm−1) IR i n t e n s i t y g (km/mol) Raman a c t i v i t y g ( A 4 /amu) I R b R a m a n c

3362
ν 13218.93218.82578.38(1802.54)28.41(0) 3 1 8 0 h sas NH str
ν 23201.33211.248.28(0.01)1126.68(1032.01) 3 1 9 3 h ss NH str
ν 33151.33065.34.97(7.27)49.50(53.58)as CH str
ν 43151.33065.30.52(1.43)281.36(272.92)3137ws CH str
ν 53133.03039.30.75(0.64)164.25(237.43)3112ws CH str
ν 63133.03039.35.02(6.87)39.47(22.30)as CH str
ν 73091.42996.74.88(0.14)453.54(555.04)3067ws CH str
ν 83091.42996.629.73(36.36)95.36(2.32)as CH str
ν 93078.32983.21.61(0.01)501.64(515.94)3052ws CH str
ν 103078.22983.163.42(60.51)27.11(0.05)as CH str
ν 113062.42970.20.17(17.58)302.47(121.90)3040ws CH str
ν 123062.42969.919.75(17.35)24.36(125.43)as CH str
ν 133059.72966.62.18(8.51)2.32(113.18)as CH str
ν 143059.62966.40.33(6.59)12.54(140.11)3019shs CH str
ν 153039.22964.54.87(0.27)148.24(30.94)3000s CH str
ν 163039.12964.515.73(0.38)28.75(42.60)as CH str
1660m
1632m
ν 171602.81551.46.25(0)50.40(53.35)1620mNH s b, CC str cr
ν 181598.71548.436.68(27.79)10.29(0)1615sNH as b,CC str cr
ν 191581.11534.227.87(34.95)13.16(0.07)1594m(CC, CN) as str pyridine
ν 201580.31533.44.33(0.03)66.13(81.74)1595m(CC, CN) s str pyridine
ν 211549.91499.80.99(0.01)28.48(30.40)1562mNH, CH s b pyridine
ν 221545.91497.757.03(43.42)6.11(0.01)1560mNH, CH as b pyridine
ν 231515.01468.14.14(0)21.16(27.48)1528wNH, CH18,20,41,39 s b
ν 241512.51466.690.78(95.24)5.73(0)1524sNH, CH18,20,41,39 as b
ν 251488.01441.340.20(42.88)17.42(0)1497mNH as b, CC str pyr
ν 261484.31436.44.55(0)111.20(172.84)1500sNH s b, CC str pyr
ν 271469.81423.51.32(0)243.81(225.53)1484vsCH20 s b, skel def CC
ν 281468.11422.09.96(7.03)56.54(0)1482wCH20 as b, skel def CC
ν 291427.91385.40.77(0)37.40(32.30)1440wNH, CH20,21,41,42 s b, skel def pyr
ν 301427.21379.49.25(10.49)6.91(0)1435wNH, CH20,21,41,42 as b, skel def pyr
ν 311414.91369.14.96(6.27)0.97(0)1428wCH17,18,19,20,38,39,40,41 as b, CC str cr
ν 321414.71366.90.84(0)9.32(13.32)1430mCH17,18,19,20,38,39,40,41 s b, CC str cr
ν 331394.61345.20.04(0)152.39(137.61)1407mNH, CH21,42 s b, CC str pyr
ν 341388.71343.633.68(37.34)17.26(0.01)1403mNH, CH21,42 as b, CC str pyr,
ν 351363.71318.7124.83(146.01)22.36(0)1386sskel def, CH as b
ν 361361.71315.920.55(0)111.09(157.34)1386sskel def, CH s b
ν 371324.11280.66.01(0)78.48(84.13)1341mskel def, CH s b
ν 381320.21277.887.62(85.48)10.37(0)1333mskel def, CH as b
ν 391291.91249.43.58(1.30)32.85(0.26)1301vwskel def, CH as b
ν 401291.31248.80.77(0)119.86(125.70)1302mskel def, CH s b
ν 411263.81225.61.51(0)13.98(24.15)1275mCH s b, C7N11, C28N32, C8C9, C29C30 str
ν 421263.41222.737.25(32.35)1.74(0)1268mCH as b, C7N11, C28N32, C8C9, C29C30 str
ν 431239.01199.91.23(24.33)2.28(0.02)1251wNH and CH s b
ν 441236.51199.824.70(0.11)0.43(4.81)1243mNH and CH as b
ν 451199.61160.31.67(0.57)0.25(0)1210wCH as b, CC str cr
ν 461199.51159.70.03(0)1.27(1.08)1210wCH s b, CC str cr
ν 471180.71140.70.58(16.59)2.52(0)1193wCH s b, CC str
ν 481180.61138.815.28(0)0.09(2.07)1193mCH s b, CC str
ν 491123.71089.28.81(10.81)0.66(0.01)1133mCH17,18,19,20 and CH38,39,40,41 as b
ν 501123.51089.11.71(0.03)2.24(2.15)1132wCH17,18,19,20 and CH38,39,40,41 s b
ν 511112.31074.60.50(25.90)1.01(0)CH15,17,18,20 and CH36,38,39,41 and NH s b
ν 521110.61074.122.51(0)0.23(4.96)1121mCH15,17,18,20 and CH36,38,39,41 and NH as b
ν 531075.61041.70.14(0)3.42(8.06)1090wskel def, CH s b
ν 541071.01035.351.41(69.84)0.35(0)1082sskel def, CH as b
ν 551056.81026.70.02(0)30.98(69.48)1075sCH15,16,36,37 s b
ν 561055.91024.64.03(3.50)2.00(0)1065wCH15,16,36,37 s b
ν 571047.81015.90.86(0)53.49(21.34)1062mskel def, CH as b
ν 581046.41012.35.31(11.68)2.32(0)1058wskel def, CH as b
ν 591008.9978.55.64(6.69)3.18(0)1025wskel def
ν 601008.6975.50.60(0)24.42(17.84)1019wskel def
ν 61968.6931.81.25(1.27)0.15(0)972vw973vwCH19-21 and CH40-42 s “oop” twisting
ν 62968.6931.70.32(0)0.04(0.24)965vw969vwCH19-21 and CH40-42 as “oop” twisting
ν 63944.2909.40.03(0)0.26(0.60)951wCH17,18,21 and CH38,39,42 as “oop” wag
ν 64944.1909.40.11(0.38)0.13(0)CH17,18,21 and CH38,39,42 as “oop” wag
ν 65938.9887.50.86(1.71)0.40(0.11)946wCH17-19,21 and CH38-40,42 as “oop” twisting
ν 66938.8887.30.76(0.28)0.41(0.66)942wCH17-19,21 and CH38-40,42 as “oop” twisting
ν 67888.4857.151.13(44.91)2.84(0)899mas skel def pyr (N11-C12-C13)
ν 68885.0851.416.47(0)26.78(25.25)890ms skel def pyr (N11-C12-C13)
ν 69872.9841.810.51(17.27)4.86(0)882mskel def, NH s twisting
ν 70871.3839.816.74(0)1.46(20.52)skel def, NH as twisting
ν 71860.9809.09.07(0)13.06(0.03)853wCH15,16,36,37 and s “oop” wag
ν 72857.2808.82.82(21.39)0.83(0)860vwCH15,16,36,37 and s “oop” wag
ν 73829.1793.11.31(43.69)0.63(0)s skel “oop” def, NH, CH wag
ν 74823.8789.65.18(0)0.65(1.24)as skel “oop” def, NH, CH wag
ν 75814.6774.0103.69(76.52)2.72(0)823m826ws NH “oop”
ν 76805.0771.89.08(0)0.45(0.73)as cr “oop” def, CH as wag
ν 77804.3735.029.08(0)0.76(0.29)801ss cr “oop” def, CH s wag
ν 78782.9733.55.92(33.11)0.03(0)as NH “oop”
ν 79764.2728.25.35(0)0.23(32.85)CH17-21,38-42 s “oop” wag
ν 80763.1727.20.29(2.50)0.05(0)CH17-21,38-42 s “oop” wag
ν 81751.2716.81.01(57.55)36.36(0)763ms “ip” skel def
ν 82750.8699.11.33(0)3.39(0.26)773m770shas “ip” skel def
ν 83727.8688.317.14(1.95)0.14(0)738m739wCH15-18 and CH36-39 “oop” s wag
ν 84726.3669.72.58(65.15)0.02(0)CH15-18 and CH36-39 “oop” as wag
ν 85696.2668.361.18(0)1.87(0.88)s “oop” skel def, CH s wag
ν 86696.1656.913.35(0)0.05(0.71)as “oop” skel def, CH s wag
ν 87678.6653.40.03(0)64.70(70.42)684vw686ss cr and pyridine ring b (sym along N1-C4, C7-C10 axis)
ν 88675.2651.115.94(14.61)1.87(0)696m696shas cr and pyridine ring b (sym along N1-C4, C7-C10 axis)
ν 89610.6589.15.28(4.30)0.01(0)as cr and pyridine ring b (asym along N1-C4, C7-C10 axis)
ν 90607.0587.81.15(0)6.13(8.11)615vw614ws cr and pyridine ring b (asym along N1-C4, C7-C10 axis)
ν 91605.3575.90.89(14.68)0.58(0)as “oop” skel def pyr
ν 92604.5572.26.17(0)2.14(0.68)602ws “oop” skel def pyr
ν 93573.7552.40.75(2.39)0.53(0)as “oop” skel def pyridine and cr
ν 94573.5547.60.55(0)0.98(2.04)571ws “oop” skel def pyridine and cr
ν 95516.2502.95.97(7.19)1.51(0)as “ip” skel def pyridine and cr
ν 96516.1500.60.74(0)8.04(10.89)524ms “ip” skel def pyridine and cr
ν 97513.7490.90.53(0)1.51(1.03)513ws “oop” skel def pyridine and cr
ν 98511.6485.20.17(0.81)0.72(0)as “oop” skel def pyridine and cr
ν 99472.8455.08.28(0)1.82(9.13)as “ip” skel def cr
ν 100471.5453.50.17(8.39)8.11(0)479ms “ip” skel def cr
ν 101430.1414.50.54(8.03)11.61(0)438ms “ip” skel def cr, CH17,19,38,40 “oop”
ν 102429.9414.37.54(0)2.59(15.89)432shas “ip” skel def cr, CH17,19,38,40 “oop”
ν 103426.3411.40.52(0)1.64(2.25)as “oop” skel def cr, CH17,19,38,40 “oop”
ν 104425.1410.30.58(2.00)4.49(0)424ws “oop” skel def cr, CH17,19,38,40 “oop”
ν 105284.4273.31.89(1.93)0.81(0)as “oop” pyridine and cr rock
ν 106283.5270.91.37(0)1.34(2.06)300ws “oop” pyridine and cr rock
ν 107252.8244.70.65(6.73)0.04(0)as “oop” pyr and cr rock
ν 108249.5238.06.20(6.29)0.17(0)s “oop” pyr and cr rock
ν 109248.8237.53.53(0)0.52(6.82)267was pyr and pyridine rings “ip” bend
ν 110243.3231.80.07(0)5.18(0.05)251ms pyr and pyridine rings “ip” bend
ν 111163.0141.80.01(0.04)0.27(0)169was pyr and pyridine tor
ν 112150.4139.10.03(0)0.43(1.24)154ms pyr and pyridine tor
ν 113122.3117.06.27(0)0.23(2.44)as “oop” pyridine and pyr rock
ν 114121.9112.33.70(6.00)0.91(0)s “oop” pyridine and pyr rock
ν 11580.275.93.58(1.02)3.54(0)dim rock
ν 11678.271.40.02(0)1.54(1.80)dim b
ν 11767.059.60.00(0)1.15(3.12)dim b
ν 11843.421.30.18(0.12)9.82(0)dim rock
ν 11926.19.20.27(0)4.96(15.09)dim rock
ν 12021.3−35.30.04(0)11.69(0)dim tor

a B 3LYP/cc-pVTZ, C2 symmetry group, scaling factor = 0 . 9 6 8 2 , as recommended in the literature [39].
b P olycrystalline sample, 293 K.
c P olycrystalline sample, 293 K, 785 nm laser (633 nm was used in the NH region).
d A bbreviations. s: symmetric; as: antisymmetric; str: stretch; b: bend; ip: in-plane; oop: out-of-plane; skel def: skeletal deformation; tor: torsion; pyrid: pyridine; pyr: pyrrole; cr: central ring.
e T wisted dimer.
f P lanar dimer.
g I n parentheses: values computed for the planar dimer.
h V ery broad (~200 cm−1).